21129959 has 2 divisors, whose sum is σ = 21129960. Its totient is φ = 21129958.

The previous prime is 21129949. The next prime is 21129961. The reversal of 21129959 is 95992112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21129959 - 2⁴ = 21129943 is a prime.

Together with 21129961, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21129949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10564979 + 10564980.

It is an arithmetic number, because the mean of its divisors is an integer number (10564980).

Almost surely, 2^21129959 is an apocalyptic number.

21129959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21129959 is an equidigital number, since it uses as much as digits as its factorization.

21129959 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 14580, while the sum is 38.

The square root of 21129959 is about 4596.7335141381. The cubic root of 21129959 is about 276.4603699141.

The spelling of 21129959 in words is "twenty-one million, one hundred twenty-nine thousand, nine hundred fifty-nine".