21331320 has 32 divisors (see below), whose sum is σ = 63994320. Its totient is φ = 5688320.

The previous prime is 21331313. The next prime is 21331333. The reversal of 21331320 is 2313312.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21331320.

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, 88761 + ... + 89000.

Almost surely, 2^21331320 is an apocalyptic number.

21331320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21331320 is an abundant number, since it is smaller than the sum of its proper divisors (42663000).

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

21331320 is a wasteful number, since it uses less digits than its factorization.

21331320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177775 (or 177771 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 15.

The square root of 21331320 is about 4618.5841986479. The cubic root of 21331320 is about 277.3357846697.

Adding to 21331320 its reverse (2313312), we get a palindrome (23644632).

The spelling of 21331320 in words is "twenty-one million, three hundred thirty-one thousand, three hundred twenty".