21646020400 has 60 divisors (see below), whose sum is σ = 52032453192. Its totient is φ = 8653765120.

The previous prime is 21646020391. The next prime is 21646020401. The reversal of 21646020400 is 402064612.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is not an unprimeable number, because it can be changed into a prime (21646020401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 787692 + ... + 814708.

Almost surely, 2^21646020400 is an apocalyptic number.

21646020400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21646020400 is an abundant number, since it is smaller than the sum of its proper divisors (30386432792).

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

21646020400 is a wasteful number, since it uses less digits than its factorization.

21646020400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29038 (or 29027 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 25.

The spelling of 21646020400 in words is "twenty-one billion, six hundred forty-six million, twenty thousand, four hundred".