7788817661 has 2 divisors, whose sum is σ = 7788817662. Its totient is φ = 7788817660.

The previous prime is 7788817637. The next prime is 7788817669. The reversal of 7788817661 is 1667188877.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7788062500 + 755161 = 88250^2 + 869^2 .

It is a cyclic number.

It is not a de Polignac number, because 7788817661 - 2¹⁸ = 7788555517 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 7788817661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7788817669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3894408830 + 3894408831.

It is an arithmetic number, because the mean of its divisors is an integer number (3894408831).

Almost surely, 2^7788817661 is an apocalyptic number.

It is an amenable number.

7788817661 is a deficient number, since it is larger than the sum of its proper divisors (1).

7788817661 is an equidigital number, since it uses as much as digits as its factorization.

7788817661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6322176, while the sum is 59.

The square root of 7788817661 is about 88254.2784288671. The cubic root of 7788817661 is about 1982.2443058920.

The spelling of 7788817661 in words is "seven billion, seven hundred eighty-eight million, eight hundred seventeen thousand, six hundred sixty-one".