66640243 has 4 divisors (see below), whose sum is σ = 67732768.
Its totient is φ = 65547720.
The previous prime is 66640237. The next prime is 66640253. The reversal of 66640243 is 34204666.
It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 34204666 = 2 ⋅17102333.
It is a cyclic number.
It is not a de Polignac number, because 66640243 - 217 = 66509171 is a prime.
It is a Duffinian number.
It is not an unprimeable number, because it can be changed into a prime (66640253) 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 3 ways as a sum of consecutive naturals, for example, 546171 + ... + 546292.
It is an arithmetic number, because the mean of its divisors is an integer number (16933192).
Almost surely, 266640243 is an apocalyptic number.
66640243 is a deficient number, since it is larger than the sum of its proper divisors (1092525).
66640243 is a wasteful number, since it uses less digits than its factorization.
66640243 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1092524.
The product of its (nonzero) digits is 20736, while the sum is 31.
The square root of 66640243 is about 8163.3475363971.
The cubic root of 66640243 is about 405.4265545995.
The spelling of 66640243 in words is "sixty-six million, six hundred forty thousand, two hundred forty-three".