21255551215564 has 72 divisors (see below), whose sum is σ = 41712962830560. Its totient is φ = 9433095501312.

The previous prime is 21255551215559. The next prime is 21255551215603. The reversal of 21255551215564 is 46551215555212.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 731497 + ... + 6560959.

It is an arithmetic number, because the mean of its divisors is an integer number (579346705980).

Almost surely, 2^{21255551215564} is an apocalyptic number.

It is an amenable number.

21255551215564 is a deficient number, since it is larger than the sum of its proper divisors (20457411614996).

21255551215564 is a wasteful number, since it uses less digits than its factorization.

21255551215564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5829599 (or 5829554 counting only the distinct ones).

The product of its digits is 3000000, while the sum is 49.

The spelling of 21255551215564 in words is "twenty-one trillion, two hundred fifty-five billion, five hundred fifty-one million, two hundred fifteen thousand, five hundred sixty-four".