21156772808 has 16 divisors (see below), whose sum is σ = 39671026560. Its totient is φ = 10577832400.

The previous prime is 21156772807. The next prime is 21156772831. The reversal of 21156772808 is 80827765112.

It is not an unprimeable number, because it can be changed into a prime (21156772807) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 125153 + ... + 240783.

It is an arithmetic number, because the mean of its divisors is an integer number (2479439160).

Almost surely, 2^21156772808 is an apocalyptic number.

It is an amenable number.

21156772808 is a deficient number, since it is larger than the sum of its proper divisors (18514253752).

21156772808 is a wasteful number, since it uses less digits than its factorization.

21156772808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138508 (or 138504 counting only the distinct ones).

The product of its (nonzero) digits is 376320, while the sum is 47.

The spelling of 21156772808 in words is "twenty-one billion, one hundred fifty-six million, seven hundred seventy-two thousand, eight hundred eight".