21990172 has 12 divisors (see below), whose sum is σ = 39301920. Its totient is φ = 10761056.

The previous prime is 21990169. The next prime is 21990179. The reversal of 21990172 is 27109912.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21990179) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 58297 + ... + 58672.

It is an arithmetic number, because the mean of its divisors is an integer number (3275160).

Almost surely, 2^21990172 is an apocalyptic number.

It is an amenable number.

21990172 is a deficient number, since it is larger than the sum of its proper divisors (17311748).

21990172 is a wasteful number, since it uses less digits than its factorization.

21990172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 117020 (or 117018 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 31.

The square root of 21990172 is about 4689.3679744716. The cubic root of 21990172 is about 280.1622019378.

The spelling of 21990172 in words is "twenty-one million, nine hundred ninety thousand, one hundred seventy-two".