20979 has 20 divisors (see below), whose sum is σ = 36784. Its totient is φ = 11664.

The previous prime is 20963. The next prime is 20981. The reversal of 20979 is 97902.

20979 = 32² + 33² + ... + 45².

It is not a de Polignac number, because 20979 - 2⁴ = 20963 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20929) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 549 + ... + 585.

2²⁰⁹⁷⁹ is an apocalyptic number.

20979 is a deficient number, since it is larger than the sum of its proper divisors (15805).

20979 is an equidigital number, since it uses as much as digits as its factorization.

20979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56 (or 47 counting only the distinct ones).

The product of its (nonzero) digits is 1134, while the sum is 27.

The square root of 20979 is about 144.8412924549. The cubic root of 20979 is about 27.5800422827.

20979 divided by its sum of digits (27) gives a palindrome (777).

It can be divided in two parts, 20 and 979, that added together give a palindrome (999).

The spelling of 20979 in words is "twenty thousand, nine hundred seventy-nine".