65666 has 4 divisors (see below), whose sum is σ = 98502. Its totient is φ = 32832.

The previous prime is 65657. The next prime is 65677. The reversal of 65666 is 66656.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 52441 + 13225 = 229^2 + 115^2 .

It is an unprimeable number.

65666 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (3) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 16415 + ... + 16418.

2⁶⁵⁶⁶⁶ is an apocalyptic number.

65666 is a deficient number, since it is larger than the sum of its proper divisors (32836).

65666 is a wasteful number, since it uses less digits than its factorization.

65666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32835.

The product of its digits is 6480, while the sum is 29.

The square root of 65666 is about 256.2537804599. The cubic root of 65666 is about 40.3441144748.

Subtracting 65666 from its reverse (66656), we obtain a triangular number (990 = T₄₄).

The spelling of 65666 in words is "sixty-five thousand, six hundred sixty-six".