7900721 has 4 divisors (see below), whose sum is σ = 8114292. Its totient is φ = 7687152.

The previous prime is 7900709. The next prime is 7900757. The reversal of 7900721 is 1270097.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5340721 + 2560000 = 2311^2 + 1600^2 .

It is a cyclic number.

It is not a de Polignac number, because 7900721 - 2¹⁸ = 7638577 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7900421) 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, 106730 + ... + 106803.

It is an arithmetic number, because the mean of its divisors is an integer number (2028573).

Almost surely, 2^7900721 is an apocalyptic number.

It is an amenable number.

7900721 is a deficient number, since it is larger than the sum of its proper divisors (213571).

7900721 is a wasteful number, since it uses less digits than its factorization.

7900721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213570.

The product of its (nonzero) digits is 882, while the sum is 26.

The square root of 7900721 is about 2810.8221217288. The cubic root of 7900721 is about 199.1692288749.

The spelling of 7900721 in words is "seven million, nine hundred thousand, seven hundred twenty-one".