21638465 has 16 divisors (see below), whose sum is σ = 27025920. Its totient is φ = 16613760.

The previous prime is 21638431. The next prime is 21638479. The reversal of 21638465 is 56483612.

It is not a de Polignac number, because 21638465 - 2⁶ = 21638401 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20726 + ... + 21744.

It is an arithmetic number, because the mean of its divisors is an integer number (1689120).

Almost surely, 2^21638465 is an apocalyptic number.

It is an amenable number.

21638465 is a deficient number, since it is larger than the sum of its proper divisors (5387455).

21638465 is a wasteful number, since it uses less digits than its factorization.

21638465 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1192.

The product of its digits is 34560, while the sum is 35.

The square root of 21638465 is about 4651.7163499078. The cubic root of 21638465 is about 278.6605456088.

The spelling of 21638465 in words is "twenty-one million, six hundred thirty-eight thousand, four hundred sixty-five".