21231116520 has 64 divisors (see below), whose sum is σ = 65414805120. Its totient is φ = 5508612864.

The previous prime is 21231116509. The next prime is 21231116539. The reversal of 21231116520 is 2561113212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2386452 + ... + 2395331.

It is an arithmetic number, because the mean of its divisors is an integer number (1022106330).

Almost surely, 2^21231116520 is an apocalyptic number.

21231116520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21231116520 is an abundant number, since it is smaller than the sum of its proper divisors (44183688600).

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

21231116520 is a wasteful number, since it uses less digits than its factorization.

21231116520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4781834 (or 4781830 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 24.

Adding to 21231116520 its reverse (2561113212), we get a palindrome (23792229732).

The spelling of 21231116520 in words is "twenty-one billion, two hundred thirty-one million, one hundred sixteen thousand, five hundred twenty".