21722891 has 2 divisors, whose sum is σ = 21722892. Its totient is φ = 21722890.

The previous prime is 21722887. The next prime is 21722929. The reversal of 21722891 is 19822712.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21722891 - 2² = 21722887 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21722801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10861445 + 10861446.

It is an arithmetic number, because the mean of its divisors is an integer number (10861446).

Almost surely, 2^21722891 is an apocalyptic number.

21722891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21722891 is an equidigital number, since it uses as much as digits as its factorization.

21722891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4032, while the sum is 32.

The square root of 21722891 is about 4660.7822304845. The cubic root of 21722891 is about 279.0224884773.

The spelling of 21722891 in words is "twenty-one million, seven hundred twenty-two thousand, eight hundred ninety-one".