21989388 has 24 divisors (see below), whose sum is σ = 51410800. Its totient is φ = 7315200.

The previous prime is 21989377. The next prime is 21989389. The reversal of 21989388 is 88398912.

It is a happy number.

It is a super-2 number, since 2×21989388² = 967066369229088, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21989389) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5688 + ... + 8736.

Almost surely, 2^21989388 is an apocalyptic number.

It is an amenable number.

21989388 is an abundant number, since it is smaller than the sum of its proper divisors (29421412).

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

21989388 is a wasteful number, since it uses less digits than its factorization.

21989388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3657 (or 3655 counting only the distinct ones).

The product of its digits is 248832, while the sum is 48.

The square root of 21989388 is about 4689.2843803719. The cubic root of 21989388 is about 280.1588724235.

The spelling of 21989388 in words is "twenty-one million, nine hundred eighty-nine thousand, three hundred eighty-eight".