21857427 has 24 divisors (see below), whose sum is σ = 33606144. Its totient is φ = 13641984.

The previous prime is 21857411. The next prime is 21857431. The reversal of 21857427 is 72475812.

It is not a de Polignac number, because 21857427 - 2⁴ = 21857411 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21857391 and 21857400.

It is not an unprimeable number, because it can be changed into a prime (21857447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 56878 + ... + 57260.

It is an arithmetic number, because the mean of its divisors is an integer number (1400256).

Almost surely, 2^21857427 is an apocalyptic number.

21857427 is a deficient number, since it is larger than the sum of its proper divisors (11748717).

21857427 is a wasteful number, since it uses less digits than its factorization.

21857427 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 779 (or 776 counting only the distinct ones).

The product of its digits is 31360, while the sum is 36.

The square root of 21857427 is about 4675.1927233003. The cubic root of 21857427 is about 279.5973250925.

The spelling of 21857427 in words is "twenty-one million, eight hundred fifty-seven thousand, four hundred twenty-seven".