91221212 has 6 divisors (see below), whose sum is σ = 159637128. Its totient is φ = 45610604.

The previous prime is 91221203. The next prime is 91221217. The reversal of 91221212 is 21212219.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91221217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 11402648 + ... + 11402655.

It is an arithmetic number, because the mean of its divisors is an integer number (26606188).

Almost surely, 2^91221212 is an apocalyptic number.

It is an amenable number.

91221212 is a deficient number, since it is larger than the sum of its proper divisors (68415916).

91221212 is a wasteful number, since it uses less digits than its factorization.

91221212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22805307 (or 22805305 counting only the distinct ones).

The product of its digits is 144, while the sum is 20.

The square root of 91221212 is about 9550.9796356185. The cubic root of 91221212 is about 450.1583179570.

It can be divided in two parts, 9 and 1221212, that added together give a palindrome (1221221).

The spelling of 91221212 in words is "ninety-one million, two hundred twenty-one thousand, two hundred twelve".