21791089 has 4 divisors (see below), whose sum is σ = 21812224. Its totient is φ = 21769956.

The previous prime is 21791087. The next prime is 21791117. The reversal of 21791089 is 98019712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21791089 - 2¹ = 21791087 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21791087) 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, 8937 + ... + 11110.

It is an arithmetic number, because the mean of its divisors is an integer number (5453056).

Almost surely, 2^21791089 is an apocalyptic number.

It is an amenable number.

21791089 is a deficient number, since it is larger than the sum of its proper divisors (21135).

21791089 is a wasteful number, since it uses less digits than its factorization.

21791089 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21134.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 21791089 is about 4668.0926511799. The cubic root of 21791089 is about 279.3141761263.

It can be divided in two parts, 2179 and 1089, that multiplied together give a triangular number (2372931 = T₂₁₇₈).

The spelling of 21791089 in words is "twenty-one million, seven hundred ninety-one thousand, eighty-nine".