21638330 has 32 divisors (see below), whose sum is σ = 45467136. Its totient is φ = 7259904.

The previous prime is 21638329. The next prime is 21638339. The reversal of 21638330 is 3383612.

It is a self number, because there is not a number n which added to its sum of digits gives 21638330.

It is not an unprimeable number, because it can be changed into a prime (21638339) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2 + ... + 6578.

It is an arithmetic number, because the mean of its divisors is an integer number (1420848).

Almost surely, 2^21638330 is an apocalyptic number.

21638330 is an abundant number, since it is smaller than the sum of its proper divisors (23828806).

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

21638330 is a wasteful number, since it uses less digits than its factorization.

21638330 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6638.

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 21638330 is about 4651.7018391122. The cubic root of 21638330 is about 278.6599660968.

The spelling of 21638330 in words is "twenty-one million, six hundred thirty-eight thousand, three hundred thirty".