20939 has 2 divisors, whose sum is σ = 20940. Its totient is φ = 20938.

The previous prime is 20929. The next prime is 20947. The reversal of 20939 is 93902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20939 - 2¹² = 16843 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (20929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10469 + 10470.

It is an arithmetic number, because the mean of its divisors is an integer number (10470).

2²⁰⁹³⁹ is an apocalyptic number.

20939 is a deficient number, since it is larger than the sum of its proper divisors (1).

20939 is an equidigital number, since it uses as much as digits as its factorization.

20939 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486, while the sum is 23.

The square root of 20939 is about 144.7031444026. The cubic root of 20939 is about 27.5625024638.

It can be divided in two parts, 20 and 939, that added together give a palindrome (959).

The spelling of 20939 in words is "twenty thousand, nine hundred thirty-nine".