20987457 has 12 divisors (see below), whose sum is σ = 29535120. Its totient is φ = 13254552.

The previous prime is 20987453. The next prime is 20987479. The reversal of 20987457 is 75478902.

It is not a de Polignac number, because 20987457 - 2² = 20987453 is a prime.

It is a hoax number, since the sum of its digits (42) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (20987453) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8607 + ... + 10772.

It is an arithmetic number, because the mean of its divisors is an integer number (2461260).

Almost surely, 2^20987457 is an apocalyptic number.

It is an amenable number.

20987457 is a deficient number, since it is larger than the sum of its proper divisors (8547663).

20987457 is a wasteful number, since it uses less digits than its factorization.

20987457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19420 (or 19401 counting only the distinct ones).

The product of its (nonzero) digits is 141120, while the sum is 42.

The square root of 20987457 is about 4581.2069370418. The cubic root of 20987457 is about 275.8374778318.

The spelling of 20987457 in words is "twenty million, nine hundred eighty-seven thousand, four hundred fifty-seven".