21958591 has 2 divisors, whose sum is σ = 21958592. Its totient is φ = 21958590.

The previous prime is 21958579. The next prime is 21958609. The reversal of 21958591 is 19585912.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21958591 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 (21958691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10979295 + 10979296.

It is an arithmetic number, because the mean of its divisors is an integer number (10979296).

Almost surely, 2^21958591 is an apocalyptic number.

21958591 is a deficient number, since it is larger than the sum of its proper divisors (1).

21958591 is an equidigital number, since it uses as much as digits as its factorization.

21958591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32400, while the sum is 40.

The square root of 21958591 is about 4685.9994664959. Note that the first 3 decimals coincide. The cubic root of 21958591 is about 280.0280201551.

The spelling of 21958591 in words is "twenty-one million, nine hundred fifty-eight thousand, five hundred ninety-one".