666431605 has 24 divisors (see below), whose sum is σ = 955439928. Its totient is φ = 444624768.

The previous prime is 666431581. The next prime is 666431617. The reversal of 666431605 is 506134666.

It can be written as a sum of positive squares in 4 ways, for example, as 353778481 + 312653124 = 18809^2 + 17682^2 .

It is not a de Polignac number, because 666431605 - 2⁷ = 666431477 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27694 + ... + 45823.

It is an arithmetic number, because the mean of its divisors is an integer number (39809997).

Almost surely, 2^666431605 is an apocalyptic number.

It is an amenable number.

666431605 is a deficient number, since it is larger than the sum of its proper divisors (289008323).

666431605 is a wasteful number, since it uses less digits than its factorization.

666431605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73573 (or 73566 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 37.

The square root of 666431605 is about 25815.3366237979. The cubic root of 666431605 is about 873.4777800267.

The spelling of 666431605 in words is "six hundred sixty-six million, four hundred thirty-one thousand, six hundred five".