21937818 has 64 divisors (see below), whose sum is σ = 54282240. Its totient is φ = 5769792.

The previous prime is 21937807. The next prime is 21937819. The reversal of 21937818 is 81873912.

It is a super-2 number, since 2×21937818² = 962535717202248, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21937819) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 29155 + ... + 29897.

It is an arithmetic number, because the mean of its divisors is an integer number (848160).

Almost surely, 2^21937818 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21937818, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27141120).

21937818 is an abundant number, since it is smaller than the sum of its proper divisors (32344422).

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

21937818 is a wasteful number, since it uses less digits than its factorization.

21937818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 811.

The product of its digits is 24192, while the sum is 39.

The square root of 21937818 is about 4683.7824458444. The cubic root of 21937818 is about 279.9396893913.

It can be divided in two parts, 2193 and 7818, that added together give a triangular number (10011 = T₁₄₁).

The spelling of 21937818 in words is "twenty-one million, nine hundred thirty-seven thousand, eight hundred eighteen".