21818172 has 48 divisors (see below), whose sum is σ = 53222400. Its totient is φ = 6948480.

The previous prime is 21818171. The next prime is 21818201. The reversal of 21818172 is 27181812.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21818171) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 32779 + ... + 33437.

It is an arithmetic number, because the mean of its divisors is an integer number (1108800).

Almost surely, 2^21818172 is an apocalyptic number.

It is an amenable number.

21818172 is an abundant number, since it is smaller than the sum of its proper divisors (31404228).

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

21818172 is a wasteful number, since it uses less digits than its factorization.

21818172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 786 (or 784 counting only the distinct ones).

The product of its digits is 1792, while the sum is 30.

The square root of 21818172 is about 4670.9926139954. The cubic root of 21818172 is about 279.4298431937.

Adding to 21818172 its reverse (27181812), we get a palindrome (48999984).

It can be divided in two parts, 2181817 and 2, that multiplied together give a palindrome (4363634).

The spelling of 21818172 in words is "twenty-one million, eight hundred eighteen thousand, one hundred seventy-two".