666197813 has 2 divisors, whose sum is σ = 666197814. Its totient is φ = 666197812.

The previous prime is 666197803. The next prime is 666197827. The reversal of 666197813 is 318791666.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 602309764 + 63888049 = 24542^2 + 7993^2 .

It is a cyclic number.

It is not a de Polignac number, because 666197813 - 2²² = 662003509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666197803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333098906 + 333098907.

It is an arithmetic number, because the mean of its divisors is an integer number (333098907).

Almost surely, 2^666197813 is an apocalyptic number.

It is an amenable number.

666197813 is a deficient number, since it is larger than the sum of its proper divisors (1).

666197813 is an equidigital number, since it uses as much as digits as its factorization.

666197813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 326592, while the sum is 47.

The square root of 666197813 is about 25810.8080656147. The cubic root of 666197813 is about 873.3756260071.

The spelling of 666197813 in words is "six hundred sixty-six million, one hundred ninety-seven thousand, eight hundred thirteen".