21211999956 has 96 divisors (see below), whose sum is σ = 64187719680. Its totient is φ = 5931613152.

The previous prime is 21211999943. The next prime is 21211999967. The reversal of 21211999956 is 65999911212.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 262960 + ... + 334023.

It is an arithmetic number, because the mean of its divisors is an integer number (668622080).

Almost surely, 2^21211999956 is an apocalyptic number.

It is an amenable number.

21211999956 is an abundant number, since it is smaller than the sum of its proper divisors (42975719724).

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

21211999956 is a wasteful number, since it uses less digits than its factorization.

21211999956 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 597050 (or 597042 counting only the distinct ones).

The product of its digits is 787320, while the sum is 54.

The spelling of 21211999956 in words is "twenty-one billion, two hundred eleven million, nine hundred ninety-nine thousand, nine hundred fifty-six".