21155155656 has 32 divisors (see below), whose sum is σ = 54593952000. Its totient is φ = 6824243520.

The previous prime is 21155155649. The next prime is 21155155663. The reversal of 21155155656 is 65655155112.

It is an interprime number because it is at equal distance from previous prime (21155155649) and next prime (21155155663).

It is a super-2 number, since 2×21155155656² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14216431 + ... + 14217918.

It is an arithmetic number, because the mean of its divisors is an integer number (1706061000).

Almost surely, 2^21155155656 is an apocalyptic number.

It is an amenable number.

21155155656 is an abundant number, since it is smaller than the sum of its proper divisors (33438796344).

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

21155155656 is a wasteful number, since it uses less digits than its factorization.

21155155656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28434389 (or 28434385 counting only the distinct ones).

The product of its digits is 225000, while the sum is 42.

The spelling of 21155155656 in words is "twenty-one billion, one hundred fifty-five million, one hundred fifty-five thousand, six hundred fifty-six".