7821728 has 12 divisors (see below), whose sum is σ = 15399090. Its totient is φ = 3910848.

The previous prime is 7821721. The next prime is 7821733. The reversal of 7821728 is 8271287.

It can be written as a sum of positive squares in only one way, i.e., 5895184 + 1926544 = 2428^2 + 1388^2 .

It is a super-2 number, since 2×7821728² = 122358857811968, which contains 22 as substring.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (7821721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 122183 + ... + 122246.

Almost surely, 2^7821728 is an apocalyptic number.

It is an amenable number.

7821728 is a deficient number, since it is larger than the sum of its proper divisors (7577362).

7821728 is a wasteful number, since it uses less digits than its factorization.

7821728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244439 (or 244431 counting only the distinct ones).

The product of its digits is 12544, while the sum is 35.

The square root of 7821728 is about 2796.7352395248. The cubic root of 7821728 is about 198.5032262862.

The spelling of 7821728 in words is "seven million, eight hundred twenty-one thousand, seven hundred twenty-eight".