By Jean Casarez, CNN

(CNN) -- Anthony Weiner, the former politician and now convicted federal sex offender, reported Monday morning to Federal Medical Center Devens, a federal prison in Ayer, Massachusetts. He will begin serving his 21 months for sexting with a minor.

According to the institution, FMC Devens is one of six federal medical centers in the country. Dzhokhar Tsarnaev, the surviving brother in the Boston bombing attack, was also originally held at FMC Devens.

While some federal inmates are transferred to Devens from other prisons when serious medical treatment is needed, Weiner was ordered to serve his term at Devons from the beginning.

In May, Weiner, 53, pleaded guilty to one charge of transferring obscene material to a minor in federal court in Manhattan. The charges stem from communications that the former congressman had with a 15-year-old girl on social media sites between January and March 2016. At his sentencing in September, Judge Denise Cote of the Southern District of New York added that at the time Weiner was communicating with the girl, he was "in contact with 19 other women."

According to a document from the Department of Justice, sex offenders make up approximately 40% of the inmate population at FMC Devens. The prison offers a sex offender treatment program described as a "voluntary, intensive, residential therapeutic program for higher risk male sex offenders."

It is not known if Weiner will participate in this program, although at his sentencing in September, Weiner's attorney Arlo Devlin-Brown argued to the court that every day for the last year Weiner had gone to treatment and that family members saw "someone trying to make himself better."

At his sentencing in September, Cote stated that Weiner's sentence carried more importance because of his previous political career.

"Because of the defendant's notoriety, there is intense interest in the defendant's plea and sentence," Cote said in court. "It could make a difference in lives and is a very significant part of this sentence."

She added, "This is a serious crime that deserves serious punishment."

Weiner's attorneys said his crimes were a "product of sickness" and maintained he wasn't a sexual predator.

"My crime was my rock bottom" Weiner said at his sentencing in court. "I am an addict," he continued. "I take complete total responsibility. I was the adult."

Weiner also was sentenced to three years of supervised release to come after his prison term. His probation terms will require him to register as a sex offender.

Weiner is the ex-husband of Huma Abedin, Hillary Clinton's former adviser. He and Abedin have a young son.