31666561 has 16 divisors (see below), whose sum is σ = 34320384. Its totient is φ = 29139264.

The previous prime is 31666553. The next prime is 31666567. The reversal of 31666561 is 16566613.

It is a cyclic number.

It is not a de Polignac number, because 31666561 - 2³ = 31666553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31666567) 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 15 ways as a sum of consecutive naturals, for example, 107931 + ... + 108223.

It is an arithmetic number, because the mean of its divisors is an integer number (2145024).

Almost surely, 2^31666561 is an apocalyptic number.

It is an amenable number.

31666561 is a deficient number, since it is larger than the sum of its proper divisors (2653823).

31666561 is a wasteful number, since it uses less digits than its factorization.

31666561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 480.

The product of its digits is 19440, while the sum is 34.

The square root of 31666561 is about 5627.3049499738. The cubic root of 31666561 is about 316.3736467039.

The spelling of 31666561 in words is "thirty-one million, six hundred sixty-six thousand, five hundred sixty-one".