665687786 has 4 divisors (see below), whose sum is σ = 998531682. Its totient is φ = 332843892.

The previous prime is 665687783. The next prime is 665687801. The reversal of 665687786 is 687786566.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 687786566 = 2 ⋅343893283.

It can be written as a sum of positive squares in only one way, i.e., 654592225 + 11095561 = 25585^2 + 3331^2 .

It is not an unprimeable number, because it can be changed into a prime (665687783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 166421945 + ... + 166421948.

Almost surely, 2^665687786 is an apocalyptic number.

665687786 is a deficient number, since it is larger than the sum of its proper divisors (332843896).

665687786 is a wasteful number, since it uses less digits than its factorization.

665687786 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332843895.

The product of its digits is 20321280, while the sum is 59.

The square root of 665687786 is about 25800.9260686511. The cubic root of 665687786 is about 873.1526897838.

The spelling of 665687786 in words is "six hundred sixty-five million, six hundred eighty-seven thousand, seven hundred eighty-six".