23191991 has 4 divisors (see below), whose sum is σ = 23202312. Its totient is φ = 23181672.

The previous prime is 23191969. The next prime is 23191997. The reversal of 23191991 is 19919132.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 23191991 - 2¹⁰ = 23190967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (23191997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 200 + ... + 6813.

It is an arithmetic number, because the mean of its divisors is an integer number (5800578).

Almost surely, 2^23191991 is an apocalyptic number.

23191991 is a deficient number, since it is larger than the sum of its proper divisors (10321).

23191991 is an equidigital number, since it uses as much as digits as its factorization.

23191991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10320.

The product of its digits is 4374, while the sum is 35.

The square root of 23191991 is about 4815.8063706922. The cubic root of 23191991 is about 285.1758061696.

The spelling of 23191991 in words is "twenty-three million, one hundred ninety-one thousand, nine hundred ninety-one".