21487872 has 108 divisors (see below), whose sum is σ = 66642576. Its totient is φ = 6128640.

The previous prime is 21487783. The next prime is 21487891. The reversal of 21487872 is 27878412.

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 21487872.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 37347 + ... + 37917.

Almost surely, 2^21487872 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 21487872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33321288).

21487872 is an abundant number, since it is smaller than the sum of its proper divisors (45154704).

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

21487872 is an equidigital number, since it uses as much as digits as its factorization.

21487872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 604 (or 583 counting only the distinct ones).

The product of its digits is 50176, while the sum is 39.

The square root of 21487872 is about 4635.5012673928. The cubic root of 21487872 is about 278.0125936706.

The spelling of 21487872 in words is "twenty-one million, four hundred eighty-seven thousand, eight hundred seventy-two".