21663138 has 32 divisors (see below), whose sum is σ = 49674240. Its totient is φ = 6169680.

The previous prime is 21663127. The next prime is 21663139. The reversal of 21663138 is 83136612.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21663139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16983 + ... + 18213.

It is an arithmetic number, because the mean of its divisors is an integer number (1552320).

Almost surely, 2^21663138 is an apocalyptic number.

21663138 is an abundant number, since it is smaller than the sum of its proper divisors (28011102).

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

21663138 is a wasteful number, since it uses less digits than its factorization.

21663138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1662.

The product of its digits is 5184, while the sum is 30.

The square root of 21663138 is about 4654.3676262195. The cubic root of 21663138 is about 278.7664184931.

It can be divided in two parts, 2166313 and 8, that added together give a triangular number (2166321 = T₂₀₈₁).

The spelling of 21663138 in words is "twenty-one million, six hundred sixty-three thousand, one hundred thirty-eight".