22991 has 4 divisors (see below), whose sum is σ = 23352. Its totient is φ = 22632.

The previous prime is 22973. The next prime is 22993. The reversal of 22991 is 19922.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 22991 - 2¹⁴ = 6607 is a prime.

It is a Duffinian number.

It is a plaindrome in base 12 and base 16.

It is a nialpdrome in base 14.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (22993) 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, 56 + ... + 221.

It is an arithmetic number, because the mean of its divisors is an integer number (5838).

2²²⁹⁹¹ is an apocalyptic number.

22991 is a deficient number, since it is larger than the sum of its proper divisors (361).

22991 is an equidigital number, since it uses as much as digits as its factorization.

22991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 360.

The product of its digits is 324, while the sum is 23.

The square root of 22991 is about 151.6278338565. The cubic root of 22991 is about 28.4349599229.

The spelling of 22991 in words is "twenty-two thousand, nine hundred ninety-one".