20856137 has 4 divisors (see below), whose sum is σ = 20907540. Its totient is φ = 20804736.

The previous prime is 20856131. The next prime is 20856181. The reversal of 20856137 is 73165802.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 73165802 = 2 ⋅36582901.

It can be written as a sum of positive squares in 2 ways, for example, as 8317456 + 12538681 = 2884^2 + 3541^2 .

It is a cyclic number.

It is not a de Polignac number, because 20856137 - 2²⁰ = 19807561 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20856131) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25088 + ... + 25905.

It is an arithmetic number, because the mean of its divisors is an integer number (5226885).

Almost surely, 2^20856137 is an apocalyptic number.

It is an amenable number.

20856137 is a deficient number, since it is larger than the sum of its proper divisors (51403).

20856137 is an equidigital number, since it uses as much as digits as its factorization.

20856137 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51402.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 20856137 is about 4566.8519792084. The cubic root of 20856137 is about 275.2609621980.

The spelling of 20856137 in words is "twenty million, eight hundred fifty-six thousand, one hundred thirty-seven".