21607720 has 32 divisors (see below), whose sum is σ = 49127400. Its totient is φ = 8552448.

The previous prime is 21607709. The next prime is 21607739. The reversal of 21607720 is 2770612.

It can be written as a sum of positive squares in 4 ways, for example, as 13439556 + 8168164 = 3666^2 + 2858^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1096 + ... + 6664.

Almost surely, 2^21607720 is an apocalyptic number.

21607720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21607720 is an abundant number, since it is smaller than the sum of its proper divisors (27519680).

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

21607720 is a wasteful number, since it uses less digits than its factorization.

21607720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5677 (or 5673 counting only the distinct ones).

The product of its (nonzero) digits is 1176, while the sum is 25.

The square root of 21607720 is about 4648.4104810139. The cubic root of 21607720 is about 278.5285048294.

The spelling of 21607720 in words is "twenty-one million, six hundred seven thousand, seven hundred twenty".