21800538 has 12 divisors (see below), whose sum is σ = 47234538. Its totient is φ = 7266840.

The previous prime is 21800521. The next prime is 21800551. The reversal of 21800538 is 83500812.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20766249 + 1034289 = 4557^2 + 1017^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 605553 + ... + 605588.

Almost surely, 2^21800538 is an apocalyptic number.

21800538 is an abundant number, since it is smaller than the sum of its proper divisors (25434000).

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

21800538 is a wasteful number, since it uses less digits than its factorization.

21800538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1211149 (or 1211146 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21800538 is about 4669.1046250861. The cubic root of 21800538 is about 279.3545421411.

The spelling of 21800538 in words is "twenty-one million, eight hundred thousand, five hundred thirty-eight".