20913 has 4 divisors (see below), whose sum is σ = 27888. Its totient is φ = 13940.

The previous prime is 20903. The next prime is 20921. The reversal of 20913 is 31902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20913 - 2⁴ = 20897 is a prime.

It is a D-number.

It is a plaindrome in base 14.

It is a junction number, because it is equal to n+sod(n) for n = 20892 and 20901.

It is not an unprimeable number, because it can be changed into a prime (20903) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3483 + ... + 3488.

It is an arithmetic number, because the mean of its divisors is an integer number (6972).

2²⁰⁹¹³ is an apocalyptic number.

It is an amenable number.

20913 is a deficient number, since it is larger than the sum of its proper divisors (6975).

20913 is an equidigital number, since it uses as much as digits as its factorization.

20913 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6974.

The product of its (nonzero) digits is 54, while the sum is 15.

The square root of 20913 is about 144.6132773987. The cubic root of 20913 is about 27.5510895998.

It can be divided in two parts, 209 and 13, that added together give a palindrome (222).

The spelling of 20913 in words is "twenty thousand, nine hundred thirteen".