21644633420 has 24 divisors (see below), whose sum is σ = 45496615248. Its totient is φ = 8649684800.

The previous prime is 21644633369. The next prime is 21644633453. The reversal of 21644633420 is 2433644612.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 488786 + ... + 531225.

It is an arithmetic number, because the mean of its divisors is an integer number (1895692302).

Almost surely, 2^21644633420 is an apocalyptic number.

21644633420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21644633420 is an abundant number, since it is smaller than the sum of its proper divisors (23851981828).

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

21644633420 is a wasteful number, since it uses less digits than its factorization.

21644633420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1021081 (or 1021079 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 35.

The spelling of 21644633420 in words is "twenty-one billion, six hundred forty-four million, six hundred thirty-three thousand, four hundred twenty".