6511511666 has 48 divisors (see below), whose sum is σ = 11417914872. Its totient is φ = 2773309440.

The previous prime is 6511511639. The next prime is 6511511707. The reversal of 6511511666 is 6661151156.

It can be written as a sum of positive squares in 4 ways, for example, as 4233454225 + 2278057441 = 65065^2 + 47729^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 955166 + ... + 961958.

Almost surely, 2^6511511666 is an apocalyptic number.

6511511666 is a deficient number, since it is larger than the sum of its proper divisors (4906403206).

6511511666 is a wasteful number, since it uses less digits than its factorization.

6511511666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7067 (or 7056 counting only the distinct ones).

The product of its digits is 32400, while the sum is 38.

The square root of 6511511666 is about 80693.9382233883. The cubic root of 6511511666 is about 1867.3566574148.

The spelling of 6511511666 in words is "six billion, five hundred eleven million, five hundred eleven thousand, six hundred sixty-six".