20856987 has 32 divisors (see below), whose sum is σ = 32175360. Its totient is φ = 13343040.

The previous prime is 20856971. The next prime is 20856989. The reversal of 20856987 is 78965802.

20856987 is a `hidden beast` number, since 2 + 0 + 8 + 569 + 87 = 666.

It is not a de Polignac number, because 20856987 - 2⁴ = 20856971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20856989) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 91768 + ... + 91994.

It is an arithmetic number, because the mean of its divisors is an integer number (1005480).

Almost surely, 2^20856987 is an apocalyptic number.

20856987 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

20856987 is a deficient number, since it is larger than the sum of its proper divisors (11318373).

20856987 is a wasteful number, since it uses less digits than its factorization.

20856987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 360 (or 354 counting only the distinct ones).

The product of its (nonzero) digits is 241920, while the sum is 45.

The square root of 20856987 is about 4566.9450401773. The cubic root of 20856987 is about 275.2647016032.

The spelling of 20856987 in words is "twenty million, eight hundred fifty-six thousand, nine hundred eighty-seven".