21742172 has 6 divisors (see below), whose sum is σ = 38048808. Its totient is φ = 10871084.

The previous prime is 21742163. The next prime is 21742187. The reversal of 21742172 is 27124712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2717768 + ... + 2717775.

It is an arithmetic number, because the mean of its divisors is an integer number (6341468).

Almost surely, 2^21742172 is an apocalyptic number.

It is an amenable number.

21742172 is a deficient number, since it is larger than the sum of its proper divisors (16306636).

21742172 is a wasteful number, since it uses less digits than its factorization.

21742172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5435547 (or 5435545 counting only the distinct ones).

The product of its digits is 1568, while the sum is 26.

The square root of 21742172 is about 4662.8502013254. The cubic root of 21742172 is about 279.1050164995.

Adding to 21742172 its reverse (27124712), we get a palindrome (48866884).

It can be divided in two parts, 2174217 and 2, that multiplied together give a palindrome (4348434).

The spelling of 21742172 in words is "twenty-one million, seven hundred forty-two thousand, one hundred seventy-two".