21998028 has 48 divisors (see below), whose sum is σ = 57689856. Its totient is φ = 6473280.

The previous prime is 21998027. The next prime is 21998033. The reversal of 21998028 is 82089912.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is not an unprimeable number, because it can be changed into a prime (21998027) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 523 + ... + 6653.

It is an arithmetic number, because the mean of its divisors is an integer number (1201872).

Almost surely, 2^21998028 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 21998028, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28844928).

21998028 is an abundant number, since it is smaller than the sum of its proper divisors (35691828).

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

21998028 is a wasteful number, since it uses less digits than its factorization.

21998028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6174 (or 6172 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 39.

The square root of 21998028 is about 4690.2055392061. The cubic root of 21998028 is about 280.1955606615.

The spelling of 21998028 in words is "twenty-one million, nine hundred ninety-eight thousand, twenty-eight".