21927791 has 4 divisors (see below), whose sum is σ = 22520472. Its totient is φ = 21335112.

The previous prime is 21927779. The next prime is 21927797. The reversal of 21927791 is 19772912.

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 21927791 - 2⁶ = 21927727 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 (21927797) 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, 296285 + ... + 296358.

It is an arithmetic number, because the mean of its divisors is an integer number (5630118).

Almost surely, 2^21927791 is an apocalyptic number.

21927791 is a deficient number, since it is larger than the sum of its proper divisors (592681).

21927791 is an equidigital number, since it uses as much as digits as its factorization.

21927791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 592680.

The product of its digits is 15876, while the sum is 38.

The square root of 21927791 is about 4682.7119279324. The cubic root of 21927791 is about 279.8970327177.

The spelling of 21927791 in words is "twenty-one million, nine hundred twenty-seven thousand, seven hundred ninety-one".