21131531540 has 24 divisors (see below), whose sum is σ = 50715676032. Its totient is φ = 7245096480.

The previous prime is 21131531527. The next prime is 21131531621. The reversal of 21131531540 is 4513513112.

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, 75469616 + ... + 75469895.

It is an arithmetic number, because the mean of its divisors is an integer number (2113153168).

Almost surely, 2^21131531540 is an apocalyptic number.

21131531540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21131531540 is an abundant number, since it is smaller than the sum of its proper divisors (29584144492).

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

21131531540 is a wasteful number, since it uses less digits than its factorization.

21131531540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150939527 (or 150939525 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 26.

The spelling of 21131531540 in words is "twenty-one billion, one hundred thirty-one million, five hundred thirty-one thousand, five hundred forty".