The eligibility is provided below -

" A Master’s degree in mathematics and related areas with minimum 55 percent marks (50 per cent marks for SC/ST/PH candidates) or an equivalent grade from a recognised university or an institution of higher learning. Candidates of this category will have to undertake course work before registration in the PhD programme. A candidate with an MPhil Degree in the relevant discipline, with minimum fifty-five percent marks (fifty percent marks for SC/ST/PH candidates) or an equivalent grade from a recognised university or an institution of higher learning need not undertake the course work".

For reference, you can go through the below link -

http://www.ignou.ac.in/ignou/aboutignou/school/sos/programmes/detail/97/1

Good Luck!!!