21887172 has 60 divisors (see below), whose sum is σ = 58585296. Its totient is φ = 7121520.

The previous prime is 21887167. The next prime is 21887179. The reversal of 21887172 is 27178812.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21887179) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 13147 + ... + 14717.

Almost surely, 2^21887172 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21887172, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29292648).

21887172 is an abundant number, since it is smaller than the sum of its proper divisors (36698124).

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

21887172 is a wasteful number, since it uses less digits than its factorization.

21887172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1630 (or 1619 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 21887172 is about 4678.3727940385. The cubic root of 21887172 is about 279.7240989755.

The spelling of 21887172 in words is "twenty-one million, eight hundred eighty-seven thousand, one hundred seventy-two".