21812404 has 6 divisors (see below), whose sum is σ = 38171714. Its totient is φ = 10906200.

The previous prime is 21812389. The next prime is 21812419. The reversal of 21812404 is 40421812.

It is an interprime number because it is at equal distance from previous prime (21812389) and next prime (21812419).

It can be written as a sum of positive squares in only one way, i.e., 11902500 + 9909904 = 3450^2 + 3148^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2726547 + ... + 2726554.

Almost surely, 2^21812404 is an apocalyptic number.

It is an amenable number.

21812404 is a deficient number, since it is larger than the sum of its proper divisors (16359310).

21812404 is a wasteful number, since it uses less digits than its factorization.

21812404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5453105 (or 5453103 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 22.

The square root of 21812404 is about 4670.3751455317. The cubic root of 21812404 is about 279.4052170337.

It can be divided in two parts, 218 and 12404, that multiplied together give a palindrome (2704072).

The spelling of 21812404 in words is "twenty-one million, eight hundred twelve thousand, four hundred four".