21108091 has 4 divisors (see below), whose sum is σ = 21317184. Its totient is φ = 20899000.

The previous prime is 21108083. The next prime is 21108097. The reversal of 21108091 is 19080112.

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 21108091 - 2³ = 21108083 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21108097) 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, 104395 + ... + 104596.

It is an arithmetic number, because the mean of its divisors is an integer number (5329296).

Almost surely, 2^21108091 is an apocalyptic number.

21108091 is a deficient number, since it is larger than the sum of its proper divisors (209093).

21108091 is a wasteful number, since it uses less digits than its factorization.

21108091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209092.

The product of its (nonzero) digits is 144, while the sum is 22.

The square root of 21108091 is about 4594.3542527759. The cubic root of 21108091 is about 276.3649647413.

It can be divided in two parts, 2110 and 8091, that added together give a palindrome (10201).

The spelling of 21108091 in words is "twenty-one million, one hundred eight thousand, ninety-one".