21531231520 has 48 divisors (see below), whose sum is σ = 50938554240. Its totient is φ = 8600468224.

The previous prime is 21531231517. The next prime is 21531231529. The reversal of 21531231520 is 2513213512.

It is not an unprimeable number, because it can be changed into a prime (21531231529) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21459 + ... + 208621.

It is an arithmetic number, because the mean of its divisors is an integer number (1061219880).

Almost surely, 2^21531231520 is an apocalyptic number.

21531231520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21531231520 is an abundant number, since it is smaller than the sum of its proper divisors (29407322720).

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

21531231520 is a wasteful number, since it uses less digits than its factorization.

21531231520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 187897 (or 187889 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 25.

The spelling of 21531231520 in words is "twenty-one billion, five hundred thirty-one million, two hundred thirty-one thousand, five hundred twenty".