21922991 has 4 divisors (see below), whose sum is σ = 22432872. Its totient is φ = 21413112.

The previous prime is 21922969. The next prime is 21922993. The reversal of 21922991 is 19922912.

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 21922991 - 2¹⁴ = 21906607 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 (21922993) 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 in 3 ways as a sum of consecutive naturals, for example, 254876 + ... + 254961.

It is an arithmetic number, because the mean of its divisors is an integer number (5608218).

Almost surely, 2^21922991 is an apocalyptic number.

21922991 is a deficient number, since it is larger than the sum of its proper divisors (509881).

21922991 is an equidigital number, since it uses as much as digits as its factorization.

21922991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 509880.

The product of its digits is 5832, while the sum is 35.

The square root of 21922991 is about 4682.1993763615. The cubic root of 21922991 is about 279.8766080459.

The spelling of 21922991 in words is "twenty-one million, nine hundred twenty-two thousand, nine hundred ninety-one".