21988128 has 48 divisors (see below), whose sum is σ = 58030560. Its totient is φ = 7289856.

The previous prime is 21988103. The next prime is 21988133. The reversal of 21988128 is 82188912.

It is a tau number, because it is divible by the number of its divisors (48).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21288 + ... + 22296.

It is an arithmetic number, because the mean of its divisors is an integer number (1208970).

Almost surely, 2^21988128 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 21988128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29015280).

21988128 is an abundant number, since it is smaller than the sum of its proper divisors (36042432).

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

21988128 is a wasteful number, since it uses less digits than its factorization.

21988128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1249 (or 1241 counting only the distinct ones).

The product of its digits is 18432, while the sum is 39.

The square root of 21988128 is about 4689.1500295896. The cubic root of 21988128 is about 280.1535212526.

The spelling of 21988128 in words is "twenty-one million, nine hundred eighty-eight thousand, one hundred twenty-eight".