21620643 has 12 divisors (see below), whose sum is σ = 31686984. Its totient is φ = 13103200.

The previous prime is 21620603. The next prime is 21620659. The reversal of 21620643 is 34602612.

It is not a de Polignac number, because 21620643 - 2⁶ = 21620579 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21620603) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29418 + ... + 30143.

It is an arithmetic number, because the mean of its divisors is an integer number (2640582).

Almost surely, 2^21620643 is an apocalyptic number.

21620643 is a deficient number, since it is larger than the sum of its proper divisors (10066341).

21620643 is a wasteful number, since it uses less digits than its factorization.

21620643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59586 (or 59575 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 24.

The square root of 21620643 is about 4649.8003182932. The cubic root of 21620643 is about 278.5840205823.

The spelling of 21620643 in words is "twenty-one million, six hundred twenty thousand, six hundred forty-three".