8661978749 has 2 divisors, whose sum is σ = 8661978750. Its totient is φ = 8661978748.

The previous prime is 8661978713. The next prime is 8661978751. The reversal of 8661978749 is 9478791668.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 7735202500 + 926776249 = 87950^2 + 30443^2 .

It is a cyclic number.

It is not a de Polignac number, because 8661978749 - 2¹⁶ = 8661913213 is a prime.

It is a Sophie Germain prime.

Together with 8661978751, it forms a pair of twin primes.

It is a Chen 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 (8661978449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4330989374 + 4330989375.

It is an arithmetic number, because the mean of its divisors is an integer number (4330989375).

Almost surely, 2^8661978749 is an apocalyptic number.

It is an amenable number.

8661978749 is a deficient number, since it is larger than the sum of its proper divisors (1).

8661978749 is an equidigital number, since it uses as much as digits as its factorization.

8661978749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36578304, while the sum is 65.

The square root of 8661978749 is about 93069.7520626331. The cubic root of 8661978749 is about 2053.7096225231.

The spelling of 8661978749 in words is "eight billion, six hundred sixty-one million, nine hundred seventy-eight thousand, seven hundred forty-nine".