21285768 has 128 divisors (see below), whose sum is σ = 66873600. Its totient is φ = 5505024.

The previous prime is 21285749. The next prime is 21285769. The reversal of 21285768 is 86758212.

It is not an unprimeable number, because it can be changed into a prime (21285769) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 82696 + ... + 82952.

It is an arithmetic number, because the mean of its divisors is an integer number (522450).

Almost surely, 2^21285768 is an apocalyptic number.

21285768 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 21285768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33436800).

21285768 is an abundant number, since it is smaller than the sum of its proper divisors (45587832).

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

21285768 is a wasteful number, since it uses less digits than its factorization.

21285768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319 (or 315 counting only the distinct ones).

The product of its digits is 53760, while the sum is 39.

The square root of 21285768 is about 4613.6501817975. The cubic root of 21285768 is about 277.1382316057.

The spelling of 21285768 in words is "twenty-one million, two hundred eighty-five thousand, seven hundred sixty-eight".