666423 has 6 divisors (see below), whose sum is σ = 962624. Its totient is φ = 444276.

The previous prime is 666403. The next prime is 666427. The reversal of 666423 is 324666.

It is not a de Polignac number, because 666423 - 2⁸ = 666167 is a prime.

It is a super-2 number, since 2×666423² = 888239229858, 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 (666427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 37015 + ... + 37032.

2⁶⁶⁶⁴²³ is an apocalyptic number.

666423 is a deficient number, since it is larger than the sum of its proper divisors (296201).

666423 is a wasteful number, since it uses less digits than its factorization.

666423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74053 (or 74050 counting only the distinct ones).

The product of its digits is 5184, while the sum is 27.

The square root of 666423 is about 816.3473525406. The cubic root of 666423 is about 87.3474020547.

It can be divided in two parts, 666 and 423, that added together give a square (1089 = 33²).

The spelling of 666423 in words is "six hundred sixty-six thousand, four hundred twenty-three".