21311959 has 2 divisors, whose sum is σ = 21311960. Its totient is φ = 21311958.

The previous prime is 21311957. The next prime is 21311981. The reversal of 21311959 is 95911312.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21311959 - 2¹ = 21311957 is a prime.

Together with 21311957, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21311959.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21311951) 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, 10655979 + 10655980.

It is an arithmetic number, because the mean of its divisors is an integer number (10655980).

Almost surely, 2^21311959 is an apocalyptic number.

21311959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21311959 is an equidigital number, since it uses as much as digits as its factorization.

21311959 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2430, while the sum is 31.

The square root of 21311959 is about 4616.4877341979. The cubic root of 21311959 is about 277.2518529447.

The spelling of 21311959 in words is "twenty-one million, three hundred eleven thousand, nine hundred fifty-nine".