7678987661 has 2 divisors, whose sum is σ = 7678987662. Its totient is φ = 7678987660.

The previous prime is 7678987571. The next prime is 7678987697. The reversal of 7678987661 is 1667898767.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 4996369225 + 2682618436 = 70685^2 + 51794^2 .

It is a cyclic number.

It is not a de Polignac number, because 7678987661 - 2¹⁸ = 7678725517 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (7678987061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3839493830 + 3839493831.

It is an arithmetic number, because the mean of its divisors is an integer number (3839493831).

Almost surely, 2^7678987661 is an apocalyptic number.

It is an amenable number.

7678987661 is a deficient number, since it is larger than the sum of its proper divisors (1).

7678987661 is an equidigital number, since it uses as much as digits as its factorization.

7678987661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 42674688, while the sum is 65.

The square root of 7678987661 is about 87629.8331677061. The cubic root of 7678987661 is about 1972.8829666737.

It can be divided in two parts, 767898766 and 1, that added together give a palindrome (767898767).

The spelling of 7678987661 in words is "seven billion, six hundred seventy-eight million, nine hundred eighty-seven thousand, six hundred sixty-one".