21804957 has 20 divisors (see below), whose sum is σ = 32737276. Its totient is φ = 14463360.

The previous prime is 21804953. The next prime is 21804961. The reversal of 21804957 is 75940812.

It is an interprime number because it is at equal distance from previous prime (21804953) and next prime (21804961).

It can be written as a sum of positive squares in 2 ways, for example, as 7584516 + 14220441 = 2754^2 + 3771^2 .

It is not a de Polignac number, because 21804957 - 2² = 21804953 is a prime.

It is a super-2 number, since 2×21804957² = 950912299543698, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21804953) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 18963 + ... + 20079.

Almost surely, 2^21804957 is an apocalyptic number.

21804957 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21804957 is a deficient number, since it is larger than the sum of its proper divisors (10932319).

21804957 is a wasteful number, since it uses less digits than its factorization.

21804957 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1370 (or 1361 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21804957 is about 4669.5778181759. The cubic root of 21804957 is about 279.3734160534.

The spelling of 21804957 in words is "twenty-one million, eight hundred four thousand, nine hundred fifty-seven".