666915397 has 4 divisors (see below), whose sum is σ = 667206540. Its totient is φ = 666624256.

The previous prime is 666915391. The next prime is 666915401. The reversal of 666915397 is 793519666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 793519666 = 2 ⋅396759833.

It can be written as a sum of positive squares in 2 ways, for example, as 384708996 + 282206401 = 19614^2 + 16799^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-666915397 is a prime.

It is a super-2 number, since 2×666915397² = 889552293511335218, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666915391) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 142108 + ... + 146725.

It is an arithmetic number, because the mean of its divisors is an integer number (166801635).

Almost surely, 2^666915397 is an apocalyptic number.

It is an amenable number.

666915397 is a deficient number, since it is larger than the sum of its proper divisors (291143).

666915397 is a wasteful number, since it uses less digits than its factorization.

666915397 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291142.

The product of its digits is 1837080, while the sum is 52.

The square root of 666915397 is about 25824.7051677265. The cubic root of 666915397 is about 873.6890942078.

The spelling of 666915397 in words is "six hundred sixty-six million, nine hundred fifteen thousand, three hundred ninety-seven".