21531504155320 has 64 divisors (see below), whose sum is σ = 51302419096320. Its totient is φ = 8104907126784.

The previous prime is 21531504155263. The next prime is 21531504155323. The reversal of 21531504155320 is 2355140513512.

It is a self number, because there is not a number n which added to its sum of digits gives 21531504155320.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21531504155323) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3068614 + ... + 7244266.

It is an arithmetic number, because the mean of its divisors is an integer number (801600298380).

Almost surely, 2^{21531504155320} is an apocalyptic number.

21531504155320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21531504155320 is an abundant number, since it is smaller than the sum of its proper divisors (29770914941000).

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

21531504155320 is a wasteful number, since it uses less digits than its factorization.

21531504155320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4183264 (or 4183260 counting only the distinct ones).

The product of its (nonzero) digits is 90000, while the sum is 37.

Adding to 21531504155320 its reverse (2355140513512), we get a palindrome (23886644668832).

The spelling of 21531504155320 in words is "twenty-one trillion, five hundred thirty-one billion, five hundred four million, one hundred fifty-five thousand, three hundred twenty".