21868640 has 48 divisors (see below), whose sum is σ = 53343360. Its totient is φ = 8463360.

The previous prime is 21868633. The next prime is 21868657. The reversal of 21868640 is 4686812.

It is a self number, because there is not a number n which added to its sum of digits gives 21868640.

It is a congruent number.

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, 2756 + ... + 7164.

It is an arithmetic number, because the mean of its divisors is an integer number (1111320).

Almost surely, 2^21868640 is an apocalyptic number.

21868640 is a gapful number since it is divisible by the number (20) 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 21868640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26671680).

21868640 is an abundant number, since it is smaller than the sum of its proper divisors (31474720).

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

21868640 is a wasteful number, since it uses less digits than its factorization.

21868640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4455 (or 4447 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 35.

The square root of 21868640 is about 4676.3917714409. The cubic root of 21868640 is about 279.6451286582.

The spelling of 21868640 in words is "twenty-one million, eight hundred sixty-eight thousand, six hundred forty".