23721991 has 2 divisors, whose sum is σ = 23721992. Its totient is φ = 23721990.

The previous prime is 23721979. The next prime is 23722001. The reversal of 23721991 is 19912732.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 23721991 - 2⁵ = 23721959 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (23721911) 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, 11860995 + 11860996.

It is an arithmetic number, because the mean of its divisors is an integer number (11860996).

Almost surely, 2^23721991 is an apocalyptic number.

23721991 is a deficient number, since it is larger than the sum of its proper divisors (1).

23721991 is an equidigital number, since it uses as much as digits as its factorization.

23721991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6804, while the sum is 34.

The square root of 23721991 is about 4870.5226618916. The cubic root of 23721991 is about 287.3318124044.

The spelling of 23721991 in words is "twenty-three million, seven hundred twenty-one thousand, nine hundred ninety-one".