666356391 has 24 divisors (see below), whose sum is σ = 1057230720. Its totient is φ = 402556176.

The previous prime is 666356381. The next prime is 666356393. The reversal of 666356391 is 193653666.

It is not a de Polignac number, because 666356391 - 2⁵ = 666356359 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666356393) 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 in 23 ways as a sum of consecutive naturals, for example, 80781 + ... + 88646.

It is an arithmetic number, because the mean of its divisors is an integer number (44051280).

Almost surely, 2^666356391 is an apocalyptic number.

666356391 is a deficient number, since it is larger than the sum of its proper divisors (390874329).

666356391 is a wasteful number, since it uses less digits than its factorization.

666356391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 169475 (or 169472 counting only the distinct ones).

The product of its digits is 524880, while the sum is 45.

The square root of 666356391 is about 25813.8798129998. The cubic root of 666356391 is about 873.4449183252. Note that the first 3 decimals are identical.

The spelling of 666356391 in words is "six hundred sixty-six million, three hundred fifty-six thousand, three hundred ninety-one".