21640573800 has 144 divisors (see below), whose sum is σ = 72739992780. Its totient is φ = 5765760000.

The previous prime is 21640573783. The next prime is 21640573817. The reversal of 21640573800 is 837504612.

21640573800 is a `hidden beast` number, since 2 + 1 + 6 + 4 + 0 + 573 + 80 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (21640573783) and next prime (21640573817).

It can be written as a sum of positive squares in 6 ways, for example, as 7123697604 + 14516876196 = 84402^2 + 120486^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 2337180 + ... + 2346420.

Almost surely, 2^21640573800 is an apocalyptic number.

21640573800 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 21640573800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36369996390).

21640573800 is an abundant number, since it is smaller than the sum of its proper divisors (51099418980).

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

21640573800 is a wasteful number, since it uses less digits than its factorization.

21640573800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10564 (or 10552 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 36.

The spelling of 21640573800 in words is "twenty-one billion, six hundred forty million, five hundred seventy-three thousand, eight hundred".