66631816 has 8 divisors (see below), whose sum is σ = 124934670. Its totient is φ = 33315904.

The previous prime is 66631813. The next prime is 66631837. The reversal of 66631816 is 61813666.

It is a happy number.

66631816 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 57304900 + 9326916 = 7570^2 + 3054^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (66631813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4164481 + ... + 4164496.

Almost surely, 2^66631816 is an apocalyptic number.

It is an amenable number.

66631816 is a deficient number, since it is larger than the sum of its proper divisors (58302854).

66631816 is a wasteful number, since it uses less digits than its factorization.

66631816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8328983 (or 8328979 counting only the distinct ones).

The product of its digits is 31104, while the sum is 37.

The square root of 66631816 is about 8162.8313715279. The cubic root of 66631816 is about 405.4094644578.

The spelling of 66631816 in words is "sixty-six million, six hundred thirty-one thousand, eight hundred sixteen".