20856537 has 12 divisors (see below), whose sum is σ = 32443684. Its totient is φ = 12834720.

The previous prime is 20856491. The next prime is 20856541. The reversal of 20856537 is 73565802.

It can be written as a sum of positive squares in 2 ways, for example, as 4888521 + 15968016 = 2211^2 + 3996^2 .

It is not a de Polignac number, because 20856537 - 2¹² = 20852441 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20855537) 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, 89014 + ... + 89247.

Almost surely, 2^20856537 is an apocalyptic number.

It is an amenable number.

20856537 is a deficient number, since it is larger than the sum of its proper divisors (11587147).

20856537 is a wasteful number, since it uses less digits than its factorization.

20856537 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 178280 (or 178277 counting only the distinct ones).

The product of its (nonzero) digits is 50400, while the sum is 36.

The square root of 20856537 is about 4566.8957728418. The cubic root of 20856537 is about 275.2627219308.

The spelling of 20856537 in words is "twenty million, eight hundred fifty-six thousand, five hundred thirty-seven".