666681397 has 2 divisors, whose sum is σ = 666681398. Its totient is φ = 666681396.

The previous prime is 666681343. The next prime is 666681419. The reversal of 666681397 is 793186666.

666681397 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 430936081 + 235745316 = 20759^2 + 15354^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-666681397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666681307) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333340698 + 333340699.

It is an arithmetic number, because the mean of its divisors is an integer number (333340699).

Almost surely, 2^666681397 is an apocalyptic number.

It is an amenable number.

666681397 is a deficient number, since it is larger than the sum of its proper divisors (1).

666681397 is an equidigital number, since it uses as much as digits as its factorization.

666681397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1959552, while the sum is 52.

The square root of 666681397 is about 25820.1742248189. The cubic root of 666681397 is about 873.5868987546.

The spelling of 666681397 in words is "six hundred sixty-six million, six hundred eighty-one thousand, three hundred ninety-seven".