66643125578 has 4 divisors (see below), whose sum is σ = 99964688370. Its totient is φ = 33321562788.

The previous prime is 66643125557. The next prime is 66643125589. The reversal of 66643125578 is 87552134666.

It is a happy number.

66643125578 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 87552134666 = 2 ⋅43776067333.

It can be written as a sum of positive squares in only one way, i.e., 36235787449 + 30407338129 = 190357^2 + 174377^2 .

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 16660781393 + ... + 16660781396.

Almost surely, 2^66643125578 is an apocalyptic number.

66643125578 is a deficient number, since it is larger than the sum of its proper divisors (33321562792).

66643125578 is a wasteful number, since it uses less digits than its factorization.

66643125578 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33321562791.

The product of its digits is 7257600, while the sum is 53.

The spelling of 66643125578 in words is "sixty-six billion, six hundred forty-three million, one hundred twenty-five thousand, five hundred seventy-eight".