21639626400 has 432 divisors, whose sum is σ = 85532400576. Its totient is φ = 4654202880.

The previous prime is 21639626369. The next prime is 21639626419. The reversal of 21639626400 is 462693612.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 4852972 + ... + 4857428.

It is an arithmetic number, because the mean of its divisors is an integer number (197991668).

Almost surely, 2^21639626400 is an apocalyptic number.

21639626400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21639626400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42766200288).

21639626400 is an abundant number, since it is smaller than the sum of its proper divisors (63892774176).

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

21639626400 is a wasteful number, since it uses less digits than its factorization.

21639626400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4521 (or 4491 counting only the distinct ones).

The product of its (nonzero) digits is 93312, while the sum is 39.

The spelling of 21639626400 in words is "twenty-one billion, six hundred thirty-nine million, six hundred twenty-six thousand, four hundred".