21956839 has 2 divisors, whose sum is σ = 21956840. Its totient is φ = 21956838.

The previous prime is 21956827. The next prime is 21956861. The reversal of 21956839 is 93865912.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21956839 - 2⁵ = 21956807 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21956795 and 21956804.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21950839) 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, 10978419 + 10978420.

It is an arithmetic number, because the mean of its divisors is an integer number (10978420).

Almost surely, 2^21956839 is an apocalyptic number.

21956839 is a deficient number, since it is larger than the sum of its proper divisors (1).

21956839 is an equidigital number, since it uses as much as digits as its factorization.

21956839 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 116640, while the sum is 43.

The square root of 21956839 is about 4685.8125229249. The cubic root of 21956839 is about 280.0205724680.

The spelling of 21956839 in words is "twenty-one million, nine hundred fifty-six thousand, eight hundred thirty-nine".