646660243 has 4 divisors (see below), whose sum is σ = 647351320. Its totient is φ = 645969168.

The previous prime is 646660213. The next prime is 646660247. The reversal of 646660243 is 342066646.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 342066646 = 2 ⋅171033323.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646660243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646660247) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 344133 + ... + 346006.

It is an arithmetic number, because the mean of its divisors is an integer number (161837830).

Almost surely, 2^646660243 is an apocalyptic number.

646660243 is a deficient number, since it is larger than the sum of its proper divisors (691077).

646660243 is an equidigital number, since it uses as much as digits as its factorization.

646660243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 691076.

The product of its (nonzero) digits is 124416, while the sum is 37.

The square root of 646660243 is about 25429.5151939631. The cubic root of 646660243 is about 864.7529529381.

The spelling of 646660243 in words is "six hundred forty-six million, six hundred sixty thousand, two hundred forty-three".