21268728 has 96 divisors (see below), whose sum is σ = 64122240. Its totient is φ = 6324480.

The previous prime is 21268727. The next prime is 21268757. The reversal of 21268728 is 82786212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21268692 and 21268701.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21268727) 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, 28650 + ... + 29382.

It is an arithmetic number, because the mean of its divisors is an integer number (667940).

Almost surely, 2^21268728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21268728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32061120).

21268728 is an abundant number, since it is smaller than the sum of its proper divisors (42853512).

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

21268728 is a wasteful number, since it uses less digits than its factorization.

21268728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 789 (or 782 counting only the distinct ones).

The product of its digits is 21504, while the sum is 36.

The square root of 21268728 is about 4611.8031180873. The cubic root of 21268728 is about 277.0642589215.

The spelling of 21268728 in words is "twenty-one million, two hundred sixty-eight thousand, seven hundred twenty-eight".