21857994 has 12 divisors (see below), whose sum is σ = 47359026. Its totient is φ = 7285992.

The previous prime is 21857993. The next prime is 21858017. The reversal of 21857994 is 49975812.

It can be written as a sum of positive squares in only one way, i.e., 20930625 + 927369 = 4575^2 + 963^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21857993) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 607149 + ... + 607184.

Almost surely, 2^21857994 is an apocalyptic number.

21857994 is an abundant number, since it is smaller than the sum of its proper divisors (25501032).

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

21857994 is a wasteful number, since it uses less digits than its factorization.

21857994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1214341 (or 1214338 counting only the distinct ones).

The product of its digits is 181440, while the sum is 45.

The square root of 21857994 is about 4675.2533621185. The cubic root of 21857994 is about 279.5997427346.

The spelling of 21857994 in words is "twenty-one million, eight hundred fifty-seven thousand, nine hundred ninety-four".