66640445 has 4 divisors (see below), whose sum is σ = 79968540. Its totient is φ = 53312352.

The previous prime is 66640423. The next prime is 66640481. The reversal of 66640445 is 54404666.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 54404666 = 2 ⋅27202333.

It can be written as a sum of positive squares in 2 ways, for example, as 22829284 + 43811161 = 4778^2 + 6619^2 .

It is a cyclic number.

It is not a de Polignac number, because 66640445 - 2⁶ = 66640381 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6664040 + ... + 6664049.

It is an arithmetic number, because the mean of its divisors is an integer number (19992135).

Almost surely, 2^66640445 is an apocalyptic number.

It is an amenable number.

66640445 is a deficient number, since it is larger than the sum of its proper divisors (13328095).

66640445 is a wasteful number, since it uses less digits than its factorization.

66640445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13328094.

The product of its (nonzero) digits is 69120, while the sum is 35.

The square root of 66640445 is about 8163.3599087631. The cubic root of 66640445 is about 405.4269642423.

The spelling of 66640445 in words is "sixty-six million, six hundred forty thousand, four hundred forty-five".