21221213508 has 36 divisors (see below), whose sum is σ = 58519105008. Its totient is φ = 6430670640.

The previous prime is 21221213479. The next prime is 21221213513. The reversal of 21221213508 is 80531212212.

It is a tau number, because it is divible by the number of its divisors (36).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 26794066 + ... + 26794857.

Almost surely, 2^21221213508 is an apocalyptic number.

It is an amenable number.

21221213508 is an abundant number, since it is smaller than the sum of its proper divisors (37297891500).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21221213508 is a wasteful number, since it uses less digits than its factorization.

21221213508 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53588944 (or 53588939 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The spelling of 21221213508 in words is "twenty-one billion, two hundred twenty-one million, two hundred thirteen thousand, five hundred eight".