7728661322209 has 3 divisors (see below), whose sum is σ = 7728664102257. Its totient is φ = 7728658542162.

The previous prime is 7728661322201. The next prime is 7728661322233. The reversal of 7728661322209 is 9022231668277.

The square root of 7728661322209 is 2780047.

It is a perfect power (a square), and thus also a powerful number.

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.

It is not a de Polignac number, because 7728661322209 - 2³ = 7728661322201 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 7728661322209.

It is not an unprimeable number, because it can be changed into a prime (7728661322201) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 1390024 + ... + 4170070.

It is an arithmetic number, because the mean of its divisors is an integer number (2576221367419).

Almost surely, 2^{7728661322209} is an apocalyptic number.

7728661322209 is the 2780047-th square number.

7728661322209 is the 1390024-th centered octagonal number.

It is an amenable number.

7728661322209 is a deficient number, since it is larger than the sum of its proper divisors (2780048).

7728661322209 is an frugal number, since it uses more digits than its factorization.

7728661322209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5560094 (or 2780047 counting only the distinct ones).

The product of its (nonzero) digits is 6096384, while the sum is 55.

The spelling of 7728661322209 in words is "seven trillion, seven hundred twenty-eight billion, six hundred sixty-one million, three hundred twenty-two thousand, two hundred nine".