666631 has 4 divisors (see below), whose sum is σ = 761872. Its totient is φ = 571392.

The previous prime is 666607. The next prime is 666637. The reversal of 666631 is 136666.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 666631 - 2⁵ = 666599 is a prime.

It is a super-2 number, since 2×666631² = 888793780322, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 666631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666637) 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, 47610 + ... + 47623.

It is an arithmetic number, because the mean of its divisors is an integer number (190468).

2⁶⁶⁶⁶³¹ is an apocalyptic number.

666631 is a deficient number, since it is larger than the sum of its proper divisors (95241).

666631 is an equidigital number, since it uses as much as digits as its factorization.

666631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95240.

The product of its digits is 3888, while the sum is 28.

The square root of 666631 is about 816.4747393521. The cubic root of 666631 is about 87.3564885607.

The spelling of 666631 in words is "six hundred sixty-six thousand, six hundred thirty-one".