7720778665 has 4 divisors (see below), whose sum is σ = 9264934404. Its totient is φ = 6176622928.

The previous prime is 7720778627. The next prime is 7720778671. The reversal of 7720778665 is 5668770277.

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 1615075344 + 6105703321 = 40188^2 + 78139^2 .

It is a cyclic number.

It is not a de Polignac number, because 7720778665 - 2⁷ = 7720778537 is a prime.

It is a super-2 number, since 2×7720778665² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 772077862 + ... + 772077871.

It is an arithmetic number, because the mean of its divisors is an integer number (2316233601).

Almost surely, 2^7720778665 is an apocalyptic number.

It is an amenable number.

7720778665 is a deficient number, since it is larger than the sum of its proper divisors (1544155739).

7720778665 is a wasteful number, since it uses less digits than its factorization.

7720778665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1544155738.

The product of its (nonzero) digits is 6914880, while the sum is 55.

The square root of 7720778665 is about 87867.9615388908. The cubic root of 7720778665 is about 1976.4554706342.

The spelling of 7720778665 in words is "seven billion, seven hundred twenty million, seven hundred seventy-eight thousand, six hundred sixty-five".