21156635764 has 48 divisors (see below), whose sum is σ = 41042776320. Its totient is φ = 9462061440.

The previous prime is 21156635749. The next prime is 21156635777. The reversal of 21156635764 is 46753665112.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1008082 + ... + 1028854.

It is an arithmetic number, because the mean of its divisors is an integer number (855057840).

Almost surely, 2^21156635764 is an apocalyptic number.

It is an amenable number.

21156635764 is a deficient number, since it is larger than the sum of its proper divisors (19886140556).

21156635764 is a wasteful number, since it uses less digits than its factorization.

21156635764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21160 (or 21158 counting only the distinct ones).

The product of its digits is 907200, while the sum is 46.

The spelling of 21156635764 in words is "twenty-one billion, one hundred fifty-six million, six hundred thirty-five thousand, seven hundred sixty-four".