666678888809 has 2 divisors, whose sum is σ = 666678888810. Its totient is φ = 666678888808.

The previous prime is 666678888781. The next prime is 666678888851. The reversal of 666678888809 is 908888876666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 338756592784 + 327922296025 = 582028^2 + 572645^2 .

It is a cyclic number.

It is not a de Polignac number, because 666678888809 - 2³⁶ = 597959412073 is a prime.

It is not a weakly prime, because it can be changed into another prime (666678888899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333339444404 + 333339444405.

It is an arithmetic number, because the mean of its divisors is an integer number (333339444405).

Almost surely, 2^666678888809 is an apocalyptic number.

It is an amenable number.

666678888809 is a deficient number, since it is larger than the sum of its proper divisors (1).

666678888809 is an equidigital number, since it uses as much as digits as its factorization.

666678888809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2675441664, while the sum is 80.

The spelling of 666678888809 in words is "six hundred sixty-six billion, six hundred seventy-eight million, eight hundred eighty-eight thousand, eight hundred nine".