21591166 has 4 divisors (see below), whose sum is σ = 32386752. Its totient is φ = 10795582.

The previous prime is 21591161. The next prime is 21591191. The reversal of 21591166 is 66119512.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21591161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5397790 + ... + 5397793.

It is an arithmetic number, because the mean of its divisors is an integer number (8096688).

Almost surely, 2^21591166 is an apocalyptic number.

21591166 is a deficient number, since it is larger than the sum of its proper divisors (10795586).

21591166 is a wasteful number, since it uses less digits than its factorization.

21591166 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10795585.

The product of its digits is 3240, while the sum is 31.

The square root of 21591166 is about 4646.6295311763. The cubic root of 21591166 is about 278.4573583622.

The spelling of 21591166 in words is "twenty-one million, five hundred ninety-one thousand, one hundred sixty-six".