21012120444 has 48 divisors (see below), whose sum is σ = 58981395200. Its totient is φ = 5687490816.

The previous prime is 21012120427. The next prime is 21012120461. The reversal of 21012120444 is 44402121012.

It is an interprime number because it is at equal distance from previous prime (21012120427) and next prime (21012120461).

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a self number, because there is not a number n which added to its sum of digits gives 21012120444.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6581149 + ... + 6584340.

Almost surely, 2^21012120444 is an apocalyptic number.

It is an amenable number.

21012120444 is an abundant number, since it is smaller than the sum of its proper divisors (37969274756).

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

21012120444 is a wasteful number, since it uses less digits than its factorization.

21012120444 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13165522 (or 13165520 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 21.

Adding to 21012120444 its reverse (44402121012), we get a palindrome (65414241456).

The spelling of 21012120444 in words is "twenty-one billion, twelve million, one hundred twenty thousand, four hundred forty-four".