21790911 has 4 divisors (see below), whose sum is σ = 29054552. Its totient is φ = 14527272.

The previous prime is 21790843. The next prime is 21790921. The reversal of 21790911 is 11909712.

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

It is not a de Polignac number, because 21790911 - 2²³ = 13402303 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 (21790921) 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, 3631816 + ... + 3631821.

It is an arithmetic number, because the mean of its divisors is an integer number (7263638).

Almost surely, 2^21790911 is an apocalyptic number.

21790911 is a deficient number, since it is larger than the sum of its proper divisors (7263641).

21790911 is an equidigital number, since it uses as much as digits as its factorization.

21790911 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7263640.

The product of its (nonzero) digits is 1134, while the sum is 30.

The square root of 21790911 is about 4668.0735855383. The cubic root of 21790911 is about 279.3134156004.

The spelling of 21790911 in words is "twenty-one million, seven hundred ninety thousand, nine hundred eleven".