21261857 has 8 divisors (see below), whose sum is σ = 21577920. Its totient is φ = 20948400.

The previous prime is 21261839. The next prime is 21261869. The reversal of 21261857 is 75816212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21261857 - 2⁸ = 21261601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21261827) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20483 + ... + 21495.

It is an arithmetic number, because the mean of its divisors is an integer number (2697240).

Almost surely, 2^21261857 is an apocalyptic number.

It is an amenable number.

21261857 is a deficient number, since it is larger than the sum of its proper divisors (316063).

21261857 is a wasteful number, since it uses less digits than its factorization.

21261857 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1303.

The product of its digits is 6720, while the sum is 32.

The square root of 21261857 is about 4611.0581215161. The cubic root of 21261857 is about 277.0344199084.

The spelling of 21261857 in words is "twenty-one million, two hundred sixty-one thousand, eight hundred fifty-seven".