660778371961 has 2 divisors, whose sum is σ = 660778371962. Its totient is φ = 660778371960.

The previous prime is 660778371901. The next prime is 660778371973. The reversal of 660778371961 is 169173877066.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 573020234361 + 87758137600 = 756981^2 + 296240^2 .

It is a cyclic number.

It is not a de Polignac number, because 660778371961 - 2¹³ = 660778363769 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 660778371961.

It is not a weakly prime, because it can be changed into another prime (660778371901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330389185980 + 330389185981.

It is an arithmetic number, because the mean of its divisors is an integer number (330389185981).

Almost surely, 2^660778371961 is an apocalyptic number.

It is an amenable number.

660778371961 is a deficient number, since it is larger than the sum of its proper divisors (1).

660778371961 is an equidigital number, since it uses as much as digits as its factorization.

660778371961 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16003008, while the sum is 61.

The spelling of 660778371961 in words is "six hundred sixty billion, seven hundred seventy-eight million, three hundred seventy-one thousand, nine hundred sixty-one".