20931539 has 4 divisors (see below), whose sum is σ = 22162824. Its totient is φ = 19700256.

The previous prime is 20931523. The next prime is 20931551. The reversal of 20931539 is 93513902.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20931539 - 2⁴ = 20931523 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20931569) 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, 615617 + ... + 615650.

It is an arithmetic number, because the mean of its divisors is an integer number (5540706).

Almost surely, 2^20931539 is an apocalyptic number.

20931539 is a deficient number, since it is larger than the sum of its proper divisors (1231285).

20931539 is a wasteful number, since it uses less digits than its factorization.

20931539 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1231284.

The product of its (nonzero) digits is 7290, while the sum is 32.

The square root of 20931539 is about 4575.0998896199. The cubic root of 20931539 is about 275.5922837781.

The spelling of 20931539 in words is "twenty million, nine hundred thirty-one thousand, five hundred thirty-nine".