20857644 has 18 divisors (see below), whose sum is σ = 52723580. Its totient is φ = 6952536.

The previous prime is 20857631. The next prime is 20857663. The reversal of 20857644 is 44675802.

20857644 is a `hidden beast` number, since 2 + 0 + 8 + 5 + 7 + 644 = 666.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 579379 = 20857644 / (2 + 0 + 8 + 5 + 7 + 6 + 4 + 4).

It is a junction number, because it is equal to n+sod(n) for n = 20857599 and 20857608.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 289654 + ... + 289725.

Almost surely, 2^20857644 is an apocalyptic number.

It is an amenable number.

20857644 is an abundant number, since it is smaller than the sum of its proper divisors (31865936).

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

20857644 is a wasteful number, since it uses less digits than its factorization.

20857644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 579389 (or 579384 counting only the distinct ones).

The product of its (nonzero) digits is 53760, while the sum is 36.

The square root of 20857644 is about 4567.0169695327. The cubic root of 20857644 is about 275.2675918738.

The spelling of 20857644 in words is "twenty million, eight hundred fifty-seven thousand, six hundred forty-four".