21839491 has 2 divisors, whose sum is σ = 21839492. Its totient is φ = 21839490.

The previous prime is 21839479. The next prime is 21839497. The reversal of 21839491 is 19493812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21839491 - 2⁵ = 21839459 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21839491.

It is not a weakly prime, because it can be changed into another prime (21839497) 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, 10919745 + 10919746.

It is an arithmetic number, because the mean of its divisors is an integer number (10919746).

Almost surely, 2^21839491 is an apocalyptic number.

21839491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21839491 is an equidigital number, since it uses as much as digits as its factorization.

21839491 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 37.

The square root of 21839491 is about 4673.2741199292. The cubic root of 21839491 is about 279.5208258478.

The spelling of 21839491 in words is "twenty-one million, eight hundred thirty-nine thousand, four hundred ninety-one".