221338728 has 96 divisors (see below), whose sum is σ = 653070600. Its totient is φ = 67313664.

The previous prime is 221338727. The next prime is 221338739. The reversal of 221338728 is 827833122.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 134513604 + 86825124 = 11598^2 + 9318^2 .

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 = 221338692 and 221338701.

It is not an unprimeable number, because it can be changed into a prime (221338727) 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 23 ways as a sum of consecutive naturals, for example, 81976 + ... + 84632.

Almost surely, 2^221338728 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 221338728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (326535300).

221338728 is an abundant number, since it is smaller than the sum of its proper divisors (431731872).

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

221338728 is a wasteful number, since it uses less digits than its factorization.

221338728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2771 (or 2764 counting only the distinct ones).

The product of its digits is 32256, while the sum is 36.

The square root of 221338728 is about 14877.4570407715. The cubic root of 221338728 is about 604.9030903676.

The spelling of 221338728 in words is "two hundred twenty-one million, three hundred thirty-eight thousand, seven hundred twenty-eight".