21640604 has 24 divisors (see below), whose sum is σ = 39747456. Its totient is φ = 10296000.

The previous prime is 21640561. The next prime is 21640607. The reversal of 21640604 is 40604612.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21640604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640607) 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, 6134 + ... + 8994.

It is an arithmetic number, because the mean of its divisors is an integer number (1656144).

Almost surely, 2^21640604 is an apocalyptic number.

It is an amenable number.

21640604 is a deficient number, since it is larger than the sum of its proper divisors (18106852).

21640604 is a wasteful number, since it uses less digits than its factorization.

21640604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2957 (or 2955 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 23.

The square root of 21640604 is about 4651.9462593628. The cubic root of 21640604 is about 278.6697273332.

The spelling of 21640604 in words is "twenty-one million, six hundred forty thousand, six hundred four".