21604172 has 6 divisors (see below), whose sum is σ = 37807308. Its totient is φ = 10802084.

The previous prime is 21604169. The next prime is 21604181. The reversal of 21604172 is 27140612.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2700518 + ... + 2700525.

It is an arithmetic number, because the mean of its divisors is an integer number (6301218).

Almost surely, 2^21604172 is an apocalyptic number.

It is an amenable number.

21604172 is a deficient number, since it is larger than the sum of its proper divisors (16203136).

21604172 is a wasteful number, since it uses less digits than its factorization.

21604172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5401047 (or 5401045 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21604172 is about 4648.0288295147. The cubic root of 21604172 is about 278.5132591482.

Adding to 21604172 its reverse (27140612), we get a palindrome (48744784).

The spelling of 21604172 in words is "twenty-one million, six hundred four thousand, one hundred seventy-two".