666531 has 12 divisors (see below), whose sum is σ = 994240. Its totient is φ = 429840.

The previous prime is 666529. The next prime is 666541. The reversal of 666531 is 135666.

666531 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 666531 - 2¹ = 666529 is a prime.

It is a super-2 number, since 2×666531² = 888527147922, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 666495 and 666504.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666511) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 916 + ... + 1473.

2⁶⁶⁶⁵³¹ is an apocalyptic number.

666531 is a deficient number, since it is larger than the sum of its proper divisors (327709).

666531 is a wasteful number, since it uses less digits than its factorization.

666531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2426 (or 2423 counting only the distinct ones).

The product of its digits is 3240, while the sum is 27.

The square root of 666531 is about 816.4134981736. The cubic root of 666531 is about 87.3521202841.

The spelling of 666531 in words is "six hundred sixty-six thousand, five hundred thirty-one".