21379 has 2 divisors, whose sum is σ = 21380. Its totient is φ = 21378.

The previous prime is 21377. The next prime is 21383. The reversal of 21379 is 97312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21379 - 2¹ = 21377 is a prime.

Together with 21377, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21377) 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 as a sum of consecutive naturals, namely, 10689 + 10690.

It is an arithmetic number, because the mean of its divisors is an integer number (10690).

2²¹³⁷⁹ is an apocalyptic number.

21379 is a deficient number, since it is larger than the sum of its proper divisors (1).

21379 is an equidigital number, since it uses as much as digits as its factorization.

21379 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 378, while the sum is 22.

The square root of 21379 is about 146.2155942436. The cubic root of 21379 is about 27.7542265564.

It can be divided in two parts, 213 and 79, that added together give a palindrome (292).

The spelling of 21379 in words is "twenty-one thousand, three hundred seventy-nine".