21518172 has 36 divisors (see below), whose sum is σ = 58578520. Its totient is φ = 6620832.

The previous prime is 21518143. The next prime is 21518197. The reversal of 21518172 is 27181512.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 22522 + ... + 23457.

Almost surely, 2^21518172 is an apocalyptic number.

It is an amenable number.

21518172 is an abundant number, since it is smaller than the sum of its proper divisors (37060348).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21518172 is a wasteful number, since it uses less digits than its factorization.

21518172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46002 (or 45997 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 21518172 is about 4638.7683710226. The cubic root of 21518172 is about 278.1432072750.

Adding to 21518172 its reverse (27181512), we get a palindrome (48699684).

The spelling of 21518172 in words is "twenty-one million, five hundred eighteen thousand, one hundred seventy-two".