21531500500 has 24 divisors (see below), whose sum is σ = 47024798184. Its totient is φ = 8612600000.

The previous prime is 21531500483. The next prime is 21531500521. The reversal of 21531500500 is 500513512.

It can be written as a sum of positive squares in 4 ways, for example, as 233600656 + 21297899844 = 15284^2 + 145938^2 .

It is a congruent number.

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, 21531001 + ... + 21532000.

It is an arithmetic number, because the mean of its divisors is an integer number (1959366591).

Almost surely, 2^21531500500 is an apocalyptic number.

21531500500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21531500500 is an abundant number, since it is smaller than the sum of its proper divisors (25493297684).

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

21531500500 is a wasteful number, since it uses less digits than its factorization.

21531500500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43063020 (or 43063008 counting only the distinct ones).

The product of its (nonzero) digits is 750, while the sum is 22.

The spelling of 21531500500 in words is "twenty-one billion, five hundred thirty-one million, five hundred thousand, five hundred".