21238818 has 32 divisors (see below), whose sum is σ = 43794432. Its totient is φ = 6862800.

The previous prime is 21238757. The next prime is 21238843. The reversal of 21238818 is 81883212.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49063 + ... + 49493.

It is an arithmetic number, because the mean of its divisors is an integer number (1368576).

Almost surely, 2^21238818 is an apocalyptic number.

21238818 is an abundant number, since it is smaller than the sum of its proper divisors (22555614).

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

21238818 is a wasteful number, since it uses less digits than its factorization.

21238818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 670.

The product of its digits is 6144, while the sum is 33.

The square root of 21238818 is about 4608.5592108597. The cubic root of 21238818 is about 276.9343204243.

The spelling of 21238818 in words is "twenty-one million, two hundred thirty-eight thousand, eight hundred eighteen".