Explanation:

Article 58 of the constitution sets the principal qualifications one must meet to be eligible to the office of the president. A President must be:
1)a citizen of India
2)of 35 years of age or above
3)qualified to become a member of the Lok Sabha
4)A person shall not be eligible for election as President if he holds any office of profit under the Government of India or the Government of any State or under any local or other authority subject to the control of any of the said Governments.
Certain office-holders, however, are permitted to stand as presidential candidates. These are:
1)The current vice-president
2)The governor of any state
3)A Minister of the Union or of any state (including prime minister and chief ministers)
In the event that the vice-president, a state governor or a minister is elected President, they are considered to have vacated their previous office on the date they begin serving as President.
A member of parliament or of a State Legislature can seek election to the office of the president but if he is elected as President, he shall be deemed to have vacated his seat in parliament or State Legislature on the date on which he enters upon his office as President [Article 59(1)].
Article 57 provides that a person who holds, or who has held, office as President shall, subject to the other provisions of this constitution, be eligible for re-election to that office.
Under The Presidential and Vice-Presidential Elections Act, 1952, a candidate to be nominated for the office of president needs 50 electors as proposers and 50 electors as seconders for his name to appear on the ballot