21990288 has 40 divisors (see below), whose sum is σ = 57406048. Its totient is φ = 7252992.

The previous prime is 21990259. The next prime is 21990337. The reversal of 21990288 is 88209912.

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, 2295 + ... + 7017.

Almost surely, 2^21990288 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 21990288, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28703024).

21990288 is an abundant number, since it is smaller than the sum of its proper divisors (35415760).

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

21990288 is a wasteful number, since it uses less digits than its factorization.

21990288 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4831 (or 4825 counting only the distinct ones).

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

The square root of 21990288 is about 4689.3803428598. The cubic root of 21990288 is about 280.1626945633.

The spelling of 21990288 in words is "twenty-one million, nine hundred ninety thousand, two hundred eighty-eight".