21139 has 2 divisors, whose sum is σ = 21140. Its totient is φ = 21138.

The previous prime is 21121. The next prime is 21143. The reversal of 21139 is 93112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21139 - 2⁵ = 21107 is a prime.

21139 is a lucky number.

It is a plaindrome in base 14.

It is a nialpdrome in base 13.

It is not a weakly prime, because it can be changed into another prime (21149) by changing a digit.

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

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569 + 10570.

It is an arithmetic number, because the mean of its divisors is an integer number (10570).

2²¹¹³⁹ is an apocalyptic number.

21139 is a deficient number, since it is larger than the sum of its proper divisors (1).

21139 is an equidigital number, since it uses as much as digits as its factorization.

21139 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54, while the sum is 16.

The square root of 21139 is about 145.3925720248. The cubic root of 21139 is about 27.6499794534.

It can be divided in two parts, 2 and 1139, that multiplied together give a triangular number (2278 = T₆₇).

The spelling of 21139 in words is "twenty-one thousand, one hundred thirty-nine".