21540172 has 6 divisors (see below), whose sum is σ = 37695308. Its totient is φ = 10770084.

The previous prime is 21540163. The next prime is 21540187. The reversal of 21540172 is 27104512.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2692518 + ... + 2692525.

Almost surely, 2^21540172 is an apocalyptic number.

It is an amenable number.

21540172 is a deficient number, since it is larger than the sum of its proper divisors (16155136).

21540172 is a wasteful number, since it uses less digits than its factorization.

21540172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5385047 (or 5385045 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 21540172 is about 4641.1390843197. The cubic root of 21540172 is about 278.2379654226.

Adding to 21540172 its reverse (27104512), we get a palindrome (48644684).

It can be divided in two parts, 2154017 and 2, that multiplied together give a palindrome (4308034).

The spelling of 21540172 in words is "twenty-one million, five hundred forty thousand, one hundred seventy-two".