20918539 has 4 divisors (see below), whose sum is σ = 21230824. Its totient is φ = 20606256.

The previous prime is 20918533. The next prime is 20918567. The reversal of 20918539 is 93581902.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 93581902 = 2 ⋅46790951.

It is a cyclic number.

It is not a de Polignac number, because 20918539 - 2³ = 20918531 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20918498 and 20918507.

It is not an unprimeable number, because it can be changed into a prime (20918531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 156042 + ... + 156175.

It is an arithmetic number, because the mean of its divisors is an integer number (5307706).

Almost surely, 2^20918539 is an apocalyptic number.

20918539 is a deficient number, since it is larger than the sum of its proper divisors (312285).

20918539 is an equidigital number, since it uses as much as digits as its factorization.

20918539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 312284.

The product of its (nonzero) digits is 19440, while the sum is 37.

The square root of 20918539 is about 4573.6789349494. The cubic root of 20918539 is about 275.5352177139.

The spelling of 20918539 in words is "twenty million, nine hundred eighteen thousand, five hundred thirty-nine".