21531644900 has 36 divisors (see below), whose sum is σ = 46734287460. Its totient is φ = 8610700800.

The previous prime is 21531644891. The next prime is 21531644923. The reversal of 21531644900 is 944613512.

It can be written as a sum of positive squares in 6 ways, for example, as 3125824 + 21528519076 = 1768^2 + 146726^2 .

It is a super-2 number, since 2×21531644900² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 466880 + ... + 510920.

Almost surely, 2^21531644900 is an apocalyptic number.

21531644900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21531644900 is an abundant number, since it is smaller than the sum of its proper divisors (25202642560).

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

21531644900 is a wasteful number, since it uses less digits than its factorization.

21531644900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 48944 (or 48937 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 35.

The spelling of 21531644900 in words is "twenty-one billion, five hundred thirty-one million, six hundred forty-four thousand, nine hundred".