21908172 has 96 divisors (see below), whose sum is σ = 63673344. Its totient is φ = 5760000.

The previous prime is 21908147. The next prime is 21908177. The reversal of 21908172 is 27180912.

It is not an unprimeable number, because it can be changed into a prime (21908177) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28797 + ... + 29547.

It is an arithmetic number, because the mean of its divisors is an integer number (663264).

Almost surely, 2^21908172 is an apocalyptic number.

21908172 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21908172, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31836672).

21908172 is an abundant number, since it is smaller than the sum of its proper divisors (41765172).

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

21908172 is a wasteful number, since it uses less digits than its factorization.

21908172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 799 (or 797 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21908172 is about 4680.6166260441. The cubic root of 21908172 is about 279.8135323109.

The spelling of 21908172 in words is "twenty-one million, nine hundred eight thousand, one hundred seventy-two".