21897288 has 96 divisors (see below), whose sum is σ = 70761600. Its totient is φ = 5981184.

The previous prime is 21897287. The next prime is 21897289. The reversal of 21897288 is 88279812.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21897287) and next prime (21897289).

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (21897283) 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, 10648 + ... + 12536.

It is an arithmetic number, because the mean of its divisors is an integer number (737100).

Almost surely, 2^21897288 is an apocalyptic number.

21897288 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 21897288, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35380800).

21897288 is an abundant number, since it is smaller than the sum of its proper divisors (48864312).

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

21897288 is a wasteful number, since it uses less digits than its factorization.

21897288 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1931 (or 1924 counting only the distinct ones).

The product of its digits is 129024, while the sum is 45.

The square root of 21897288 is about 4679.4538142822. The cubic root of 21897288 is about 279.7671874286.

The spelling of 21897288 in words is "twenty-one million, eight hundred ninety-seven thousand, two hundred eighty-eight".