21720612 has 24 divisors (see below), whose sum is σ = 50885856. Its totient is φ = 7211008.

The previous prime is 21720599. The next prime is 21720613. The reversal of 21720612 is 21602712.

It is not an unprimeable number, because it can be changed into a prime (21720613) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 438 + ... + 6605.

It is an arithmetic number, because the mean of its divisors is an integer number (2120244).

Almost surely, 2^21720612 is an apocalyptic number.

It is an amenable number.

21720612 is an abundant number, since it is smaller than the sum of its proper divisors (29165244).

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

21720612 is a wasteful number, since it uses less digits than its factorization.

21720612 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7307 (or 7305 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 21720612 is about 4660.5377372145. The cubic root of 21720612 is about 279.0127304991.

The spelling of 21720612 in words is "twenty-one million, seven hundred twenty thousand, six hundred twelve".