666787666 has 4 divisors (see below), whose sum is σ = 1000181502. Its totient is φ = 333393832.

The previous prime is 666787661. The next prime is 666787669.

666787666 is nontrivially palindromic in base 10.

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., 403407225 + 263380441 = 20085^2 + 16229^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 666787666.

It is not an unprimeable number, because it can be changed into a prime (666787661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 166696915 + ... + 166696918.

Almost surely, 2^666787666 is an apocalyptic number.

666787666 is a deficient number, since it is larger than the sum of its proper divisors (333393836).

666787666 is a wasteful number, since it uses less digits than its factorization.

666787666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333393835.

The product of its digits is 18289152, while the sum is 58.

The square root of 666787666 is about 25822.2320104208. The cubic root of 666787666 is about 873.6333128661.

The spelling of 666787666 in words is "six hundred sixty-six million, seven hundred eighty-seven thousand, six hundred sixty-six".