21251166 has 32 divisors (see below), whose sum is σ = 43400448. Its totient is φ = 6936000.

The previous prime is 21251141. The next prime is 21251179. The reversal of 21251166 is 66115212.

It is a super-2 number, since 2×21251166² = 903224112719112, which contains 22 as substring.

It is a plaindrome in base 16.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 84541 + ... + 84791.

It is an arithmetic number, because the mean of its divisors is an integer number (1356264).

Almost surely, 2^21251166 is an apocalyptic number.

21251166 is an abundant number, since it is smaller than the sum of its proper divisors (22149282).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21251166 is a wasteful number, since it uses less digits than its factorization.

21251166 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 496.

The product of its digits is 720, while the sum is 24.

The square root of 21251166 is about 4609.8986973685. The cubic root of 21251166 is about 276.9879788169.

Adding to 21251166 its reverse (66115212), we get a palindrome (87366378).

The spelling of 21251166 in words is "twenty-one million, two hundred fifty-one thousand, one hundred sixty-six".