668991578 has 4 divisors (see below), whose sum is σ = 1003487370. Its totient is φ = 334495788.

The previous prime is 668991569. The next prime is 668991611. The reversal of 668991578 is 875199866.

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., 501625609 + 167365969 = 22397^2 + 12937^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 167247893 + ... + 167247896.

Almost surely, 2^668991578 is an apocalyptic number.

668991578 is a deficient number, since it is larger than the sum of its proper divisors (334495792).

668991578 is a wasteful number, since it uses less digits than its factorization.

668991578 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 334495791.

The product of its digits is 6531840, while the sum is 59.

The square root of 668991578 is about 25864.8715055768. The cubic root of 668991578 is about 874.5947851075.

The spelling of 668991578 in words is "six hundred sixty-eight million, nine hundred ninety-one thousand, five hundred seventy-eight".