21284272 has 30 divisors (see below), whose sum is σ = 43816268. Its totient is φ = 10013952.

The previous prime is 21284251. The next prime is 21284273. The reversal of 21284272 is 27248212.

It is a self number, because there is not a number n which added to its sum of digits gives 21284272.

It is not an unprimeable number, because it can be changed into a prime (21284273) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 2323 + ... + 6925.

Almost surely, 2^21284272 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 21284272, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21908134).

21284272 is an abundant number, since it is smaller than the sum of its proper divisors (22531996).

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

21284272 is a wasteful number, since it uses less digits than its factorization.

21284272 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4645 (or 4622 counting only the distinct ones).

The product of its digits is 3584, while the sum is 28.

The square root of 21284272 is about 4613.4880513555. The cubic root of 21284272 is about 277.1317388714.

It can be divided in two parts, 2128 and 4272, that added together give a square (6400 = 80²).

The spelling of 21284272 in words is "twenty-one million, two hundred eighty-four thousand, two hundred seventy-two".