21638825 has 24 divisors (see below), whose sum is σ = 29164800. Its totient is φ = 15831360.

The previous prime is 21638819. The next prime is 21638831. The reversal of 21638825 is 52883612.

It is an interprime number because it is at equal distance from previous prime (21638819) and next prime (21638831).

It is not a de Polignac number, because 21638825 - 2⁴ = 21638809 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 44936 + ... + 45414.

It is an arithmetic number, because the mean of its divisors is an integer number (1215200).

Almost surely, 2^21638825 is an apocalyptic number.

21638825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21638825 is a deficient number, since it is larger than the sum of its proper divisors (7525975).

21638825 is a wasteful number, since it uses less digits than its factorization.

21638825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 641 (or 636 counting only the distinct ones).

The product of its digits is 23040, while the sum is 35.

The square root of 21638825 is about 4651.7550451416. The cubic root of 21638825 is about 278.6620909624.

The spelling of 21638825 in words is "twenty-one million, six hundred thirty-eight thousand, eight hundred twenty-five".