21986172 has 72 divisors (see below), whose sum is σ = 60540480. Its totient is φ = 6687360.

The previous prime is 21986143. The next prime is 21986191. The reversal of 21986172 is 27168912.

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

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 50797 + ... + 51227.

It is an arithmetic number, because the mean of its divisors is an integer number (840840).

Almost surely, 2^21986172 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 21986172, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30270240).

21986172 is an abundant number, since it is smaller than the sum of its proper divisors (38554308).

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

21986172 is a wasteful number, since it uses less digits than its factorization.

21986172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 563 (or 558 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21986172 is about 4688.9414583678. The cubic root of 21986172 is about 280.1452137918.

The spelling of 21986172 in words is "twenty-one million, nine hundred eighty-six thousand, one hundred seventy-two".