66431661 has 4 divisors (see below), whose sum is σ = 88575552. Its totient is φ = 44287772.

The previous prime is 66431611. The next prime is 66431669. The reversal of 66431661 is 16613466.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 66431661 - 2²¹ = 64334509 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66431669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11071941 + ... + 11071946.

It is an arithmetic number, because the mean of its divisors is an integer number (22143888).

Almost surely, 2^66431661 is an apocalyptic number.

It is an amenable number.

66431661 is a deficient number, since it is larger than the sum of its proper divisors (22143891).

66431661 is a wasteful number, since it uses less digits than its factorization.

66431661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22143890.

The product of its digits is 15552, while the sum is 33.

The square root of 66431661 is about 8150.5620051626. The cubic root of 66431661 is about 405.0031214513.

The spelling of 66431661 in words is "sixty-six million, four hundred thirty-one thousand, six hundred sixty-one".