7890721 has 4 divisors (see below), whose sum is σ = 7899012. Its totient is φ = 7882432.

The previous prime is 7890713. The next prime is 7890733. The reversal of 7890721 is 1270987.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1270987 = 37 ⋅34351.

It can be written as a sum of positive squares in 2 ways, for example, as 1234321 + 6656400 = 1111^2 + 2580^2 .

It is a cyclic number.

It is not a de Polignac number, because 7890721 - 2³ = 7890713 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

7890721 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (7810721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2500 + ... + 4693.

It is an arithmetic number, because the mean of its divisors is an integer number (1974753).

Almost surely, 2^7890721 is an apocalyptic number.

It is an amenable number.

7890721 is a deficient number, since it is larger than the sum of its proper divisors (8291).

7890721 is a wasteful number, since it uses less digits than its factorization.

7890721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8290.

The product of its (nonzero) digits is 7056, while the sum is 34.

The square root of 7890721 is about 2809.0427195043. The cubic root of 7890721 is about 199.0851634172.

The spelling of 7890721 in words is "seven million, eight hundred ninety thousand, seven hundred twenty-one".