21012799556 has 18 divisors (see below), whose sum is σ = 42776056638. Its totient is φ = 9005485440.

The previous prime is 21012799547. The next prime is 21012799559. The reversal of 21012799556 is 65599721012.

It can be written as a sum of positive squares in only one way, i.e., 17853235456 + 3159564100 = 133616^2 + 56210^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21012799556.

It is not an unprimeable number, because it can be changed into a prime (21012799559) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 53603885 + ... + 53604276.

It is an arithmetic number, because the mean of its divisors is an integer number (2376447591).

Almost surely, 2^21012799556 is an apocalyptic number.

It is an amenable number.

21012799556 is an abundant number, since it is smaller than the sum of its proper divisors (21763257082).

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

21012799556 is a wasteful number, since it uses less digits than its factorization.

21012799556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107208179 (or 107208170 counting only the distinct ones).

The product of its (nonzero) digits is 340200, while the sum is 47.

The spelling of 21012799556 in words is "twenty-one billion, twelve million, seven hundred ninety-nine thousand, five hundred fifty-six".