21821328 has 30 divisors (see below), whose sum is σ = 61069814. Its totient is φ = 7273728.

The previous prime is 21821321. The next prime is 21821333. The reversal of 21821328 is 82312812.

It can be written as a sum of positive squares in only one way, i.e., 19607184 + 2214144 = 4428^2 + 1488^2 .

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

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 (21821321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 75625 + ... + 75912.

Almost surely, 2^21821328 is an apocalyptic number.

It is an amenable number.

21821328 is an abundant number, since it is smaller than the sum of its proper divisors (39248486).

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

21821328 is a wasteful number, since it uses less digits than its factorization.

21821328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151551 (or 151542 counting only the distinct ones).

The product of its digits is 1536, while the sum is 27.

The square root of 21821328 is about 4671.3304314724. The cubic root of 21821328 is about 279.4433157258.

The spelling of 21821328 in words is "twenty-one million, eight hundred twenty-one thousand, three hundred twenty-eight".