21138959 has 2 divisors, whose sum is σ = 21138960. Its totient is φ = 21138958.

The previous prime is 21138937. The next prime is 21138977. The reversal of 21138959 is 95983112.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21138959 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21138989) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569479 + 10569480.

It is an arithmetic number, because the mean of its divisors is an integer number (10569480).

Almost surely, 2^21138959 is an apocalyptic number.

21138959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138959 is an equidigital number, since it uses as much as digits as its factorization.

21138959 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19440, while the sum is 38.

The square root of 21138959 is about 4597.7123659490. The cubic root of 21138959 is about 276.4996157727.

The spelling of 21138959 in words is "twenty-one million, one hundred thirty-eight thousand, nine hundred fifty-nine".