21129984 has 90 divisors (see below), whose sum is σ = 63067620. Its totient is φ = 7036416.

The previous prime is 21129961. The next prime is 21129989. The reversal of 21129984 is 48992112.

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

It is a nude number because it is divisible by every one of its digits and also a Zuckerman number because it is divisible by the product of its digits.

It is not an unprimeable number, because it can be changed into a prime (21129989) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 20227 + ... + 21245.

Almost surely, 2^21129984 is an apocalyptic number.

21129984 is a gapful number since it is divisible by the number (24) 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 21129984, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31533810).

21129984 is an abundant number, since it is smaller than the sum of its proper divisors (41937636).

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

21129984 is an equidigital number, since it uses as much as digits as its factorization.

21129984 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1047 (or 1024 counting only the distinct ones).

The product of its digits is 10368, while the sum is 36.

The square root of 21129984 is about 4596.7362334596. The cubic root of 21129984 is about 276.4604789458.

The spelling of 21129984 in words is "twenty-one million, one hundred twenty-nine thousand, nine hundred eighty-four".