21989688 has 96 divisors (see below), whose sum is σ = 66940800. Its totient is φ = 5880384.

The previous prime is 21989659. The next prime is 21989689. The reversal of 21989688 is 88698912.

It is a self number, because there is not a number n which added to its sum of digits gives 21989688.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21989689) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 264895 + ... + 264977.

It is an arithmetic number, because the mean of its divisors is an integer number (697300).

Almost surely, 2^21989688 is an apocalyptic number.

21989688 is a gapful number since it is divisible by the number (28) 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 21989688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33470400).

21989688 is an abundant number, since it is smaller than the sum of its proper divisors (44951112).

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

21989688 is a wasteful number, since it uses less digits than its factorization.

21989688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 201 (or 114 counting only the distinct ones).

The product of its digits is 497664, while the sum is 51.

The square root of 21989688 is about 4689.3163680861. The cubic root of 21989688 is about 280.1601464817.

The spelling of 21989688 in words is "twenty-one million, nine hundred eighty-nine thousand, six hundred eighty-eight".