66665645 has 8 divisors (see below), whose sum is σ = 80102520. Its totient is φ = 53263360.

The previous prime is 66665633. The next prime is 66665647. The reversal of 66665645 is 54656666.

It can be written as a sum of positive squares in 4 ways, for example, as 14638276 + 52027369 = 3826^2 + 7213^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 66665645 - 2⁴ = 66665629 is a prime.

It is a super-3 number, since 3×66665645³ (a number of 24 digits) contains 333 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 66665596 and 66665605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66665647) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 4196 + ... + 12285.

It is an arithmetic number, because the mean of its divisors is an integer number (10012815).

Almost surely, 2^66665645 is an apocalyptic number.

It is an amenable number.

66665645 is a deficient number, since it is larger than the sum of its proper divisors (13436875).

66665645 is a wasteful number, since it uses less digits than its factorization.

66665645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17295.

The product of its digits is 777600, while the sum is 44.

The square root of 66665645 is about 8164.9032449870. The cubic root of 66665645 is about 405.4780617000.

The spelling of 66665645 in words is "sixty-six million, six hundred sixty-five thousand, six hundred forty-five".