66685778 has 4 divisors (see below), whose sum is σ = 100028670. Its totient is φ = 33342888.

The previous prime is 66685777. The next prime is 66685793. The reversal of 66685778 is 87758666.

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., 66471409 + 214369 = 8153^2 + 463^2 .

It is not an unprimeable number, because it can be changed into a prime (66685771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 16671443 + ... + 16671446.

Almost surely, 2^66685778 is an apocalyptic number.

66685778 is a deficient number, since it is larger than the sum of its proper divisors (33342892).

66685778 is a wasteful number, since it uses less digits than its factorization.

66685778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33342891.

The product of its digits is 3386880, while the sum is 53.

The square root of 66685778 is about 8166.1360507893. The cubic root of 66685778 is about 405.5188756663.

The spelling of 66685778 in words is "sixty-six million, six hundred eighty-five thousand, seven hundred seventy-eight".