7728721 has 24 divisors (see below), whose sum is σ = 10571904. Its totient is φ = 5554080.

The previous prime is 7728709. The next prime is 7728739. The reversal of 7728721 is 1278277.

It is not a de Polignac number, because 7728721 - 2⁵ = 7728689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (7728701) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6456 + ... + 7558.

It is an arithmetic number, because the mean of its divisors is an integer number (440496).

Almost surely, 2^7728721 is an apocalyptic number.

It is an amenable number.

7728721 is a deficient number, since it is larger than the sum of its proper divisors (2843183).

7728721 is a wasteful number, since it uses less digits than its factorization.

7728721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1141 (or 1134 counting only the distinct ones).

The product of its digits is 10976, while the sum is 34.

The square root of 7728721 is about 2780.0577332135. The cubic root of 7728721 is about 197.7132962396.

The spelling of 7728721 in words is "seven million, seven hundred twenty-eight thousand, seven hundred twenty-one".