21968172 has 72 divisors (see below), whose sum is σ = 58430736. Its totient is φ = 7216128.

The previous prime is 21968171. The next prime is 21968183. The reversal of 21968172 is 27186912.

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 (21968171) 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 23 ways as a sum of consecutive naturals, for example, 94168 + ... + 94400.

It is an arithmetic number, because the mean of its divisors is an integer number (811538).

Almost surely, 2^21968172 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 21968172, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29215368).

21968172 is an abundant number, since it is smaller than the sum of its proper divisors (36462564).

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

21968172 is a wasteful number, since it uses less digits than its factorization.

21968172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 349 (or 335 counting only the distinct ones).

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

The square root of 21968172 is about 4687.0216555932. The cubic root of 21968172 is about 280.0687416256.

The spelling of 21968172 in words is "twenty-one million, nine hundred sixty-eight thousand, one hundred seventy-two".