21638890 has 96 divisors (see below), whose sum is σ = 50561280. Its totient is φ = 6604416.

The previous prime is 21638887. The next prime is 21638917. The reversal of 21638890 is 9883612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 273871 + ... + 273949.

It is an arithmetic number, because the mean of its divisors is an integer number (526680).

Almost surely, 2^21638890 is an apocalyptic number.

21638890 is an abundant number, since it is smaller than the sum of its proper divisors (28922390).

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

21638890 is a wasteful number, since it uses less digits than its factorization.

21638890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156 (or 149 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 21638890 is about 4651.7620317467. The cubic root of 21638890 is about 278.6623699828.

The spelling of 21638890 in words is "twenty-one million, six hundred thirty-eight thousand, eight hundred ninety".