666642531 has 16 divisors (see below), whose sum is σ = 936803840. Its totient is φ = 420513120.

The previous prime is 666642503. The next prime is 666642553. The reversal of 666642531 is 135246666.

666642531 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 666642531 - 2⁹ = 666642019 is a prime.

It is a super-2 number, since 2×666642531² = 888824528276171922, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 666642531.

It is not an unprimeable number, because it can be changed into a prime (666642731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 41766 + ... + 55476.

It is an arithmetic number, because the mean of its divisors is an integer number (58550240).

Almost surely, 2^666642531 is an apocalyptic number.

666642531 is a deficient number, since it is larger than the sum of its proper divisors (270161309).

666642531 is a wasteful number, since it uses less digits than its factorization.

666642531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14586.

The product of its digits is 155520, while the sum is 39.

The square root of 666642531 is about 25819.4215853105. The cubic root of 666642531 is about 873.5699223856.

The spelling of 666642531 in words is "six hundred sixty-six million, six hundred forty-two thousand, five hundred thirty-one".