21118172 has 6 divisors (see below), whose sum is σ = 36956808. Its totient is φ = 10559084.

The previous prime is 21118171. The next prime is 21118183. The reversal of 21118172 is 27181112.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21118171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2639768 + ... + 2639775.

It is an arithmetic number, because the mean of its divisors is an integer number (6159468).

Almost surely, 2^21118172 is an apocalyptic number.

It is an amenable number.

21118172 is a deficient number, since it is larger than the sum of its proper divisors (15838636).

21118172 is a wasteful number, since it uses less digits than its factorization.

21118172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5279547 (or 5279545 counting only the distinct ones).

The product of its digits is 224, while the sum is 23.

The square root of 21118172 is about 4595.4512292048. The cubic root of 21118172 is about 276.4089540627.

Adding to 21118172 its reverse (27181112), we get a palindrome (48299284).

The spelling of 21118172 in words is "twenty-one million, one hundred eighteen thousand, one hundred seventy-two".