21991185 has 24 divisors (see below), whose sum is σ = 38660544. Its totient is φ = 11561760.

The previous prime is 21991163. The next prime is 21991199. The reversal of 21991185 is 58119912.

It is not a de Polignac number, because 21991185 - 2¹⁹ = 21466897 is a prime.

It is a super-2 number, since 2×21991185² = 967224435408450, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 247 + ... + 6636.

It is an arithmetic number, because the mean of its divisors is an integer number (1610856).

Almost surely, 2^21991185 is an apocalyptic number.

It is an amenable number.

21991185 is a deficient number, since it is larger than the sum of its proper divisors (16669359).

21991185 is a wasteful number, since it uses less digits than its factorization.

21991185 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6965 (or 6962 counting only the distinct ones).

The product of its digits is 6480, while the sum is 36.

The square root of 21991185 is about 4689.4759835188. The cubic root of 21991185 is about 280.1665038589.

The spelling of 21991185 in words is "twenty-one million, nine hundred ninety-one thousand, one hundred eighty-five".