He was also given a life sentence with a minimum of 10 years at London's Old Bailey court for raping a two-year-old girl but will serve the longer of the two sentences.
The Baby P case sparked outrage after it emerged that social workers, doctors and police failed to spot the abuse despite seeing him at least 60 times over eight months.
Baby P, who can now be named as Peter, was 17 months old when his body was found in a blood-spattered cot at his home in Haringey, London, in August 2007. He had suffered fractured ribs and a broken back among more than 50 injuries.
Judge Stephen Kramer said the toddler had died "in horrific circumstances with injuries that can only have caused great pain and distress prior to his death."
He added: "Any decent person who heard the catalogue of medical conditions and non-accidental injuries suffered by Peter cannot fail to have been appalled."
He told the boy's mother she was a "manipulative and self-centred person, with a calculating side as well as a temper", who had "actively deceived" the authorities in order to protect her boyfriend.
Neither can be named for legal reasons.
On Thursday, the mother had made a last-minute plea to the court, in a letter in which she apologised for failing her dead son.
"I have lost all I hold dear to me. Now every day of my life is full of guilt... I am truly sorry," she said.
The couple's lodger Jason Owen, 37, was given an indeterminate sentence for failing to prevent the boy's death and was told he would spend at least three years behind bars.
The jail terms were criticised by the National Society For The Prevention Of Cruelty To Children (NSPCC) charity, which said they were too short.
"Baby Peter suffered sustained abuse leaving him with horrendous injuries," said chief executive Andrew Flanagan. "Two of his abusers could walk free at a time when Peter should be a schoolboy with a new world in front of him."
On Friday, a second review of the way the case was handled by local authorities found the boy's death "could and should" have been prevented.
Doctors, lawyers, police and social workers should have been able to stop the abuse "in its tracks at the first serious incident," the report concluded.
Even though the boy was placed under a child protection plan because of concerns about his care, his case was regarded as routine "with injuries expected as a matter of course."
The children services director of Haringey Council and four other employees were sacked over the death. Two doctors involved in the case have been suspended.
Lord William Laming, who headed a nationwide review of child protection services after Baby P's death, voiced confidence that wide-ranging reforms to the system for protecting vulnerable children would now be introduced.
He said the case had generated "shock and concern" because of the failure of the public services "to intervene and protect these young children already identified to be seriously at risk."
"I am confident that the recommendations I have made will be implemented fully and will produce the step change needed to improve children's services across the whole of the country," he said.
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