21288172 has 24 divisors (see below), whose sum is σ = 38744496. Its totient is φ = 10225728.

The previous prime is 21288167. The next prime is 21288173. The reversal of 21288172 is 27188212.

It is not an unprimeable number, because it can be changed into a prime (21288173) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11418 + ... + 13150.

It is an arithmetic number, because the mean of its divisors is an integer number (1614354).

Almost surely, 2^21288172 is an apocalyptic number.

It is an amenable number.

21288172 is a deficient number, since it is larger than the sum of its proper divisors (17456324).

21288172 is a wasteful number, since it uses less digits than its factorization.

21288172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1857 (or 1855 counting only the distinct ones).

The product of its digits is 3584, while the sum is 31.

The square root of 21288172 is about 4613.9107056812. The cubic root of 21288172 is about 277.1486644801.

The spelling of 21288172 in words is "twenty-one million, two hundred eighty-eight thousand, one hundred seventy-two".