665823643 has 2 divisors, whose sum is σ = 665823644. Its totient is φ = 665823642.

The previous prime is 665823607. The next prime is 665823659. The reversal of 665823643 is 346328566.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 665823643 - 2²⁹ = 128952731 is a prime.

It is a super-2 number, since 2×665823643² = 886642247155582898, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 665823643.

It is not a weakly prime, because it can be changed into another prime (665823043) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332911821 + 332911822.

It is an arithmetic number, because the mean of its divisors is an integer number (332911822).

Almost surely, 2^665823643 is an apocalyptic number.

665823643 is a deficient number, since it is larger than the sum of its proper divisors (1).

665823643 is an equidigital number, since it uses as much as digits as its factorization.

665823643 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 622080, while the sum is 43.

The square root of 665823643 is about 25803.5587274314. The cubic root of 665823643 is about 873.2120849129.

It can be divided in two parts, 66582 and 3643, that added together give a square (70225 = 265²).

The spelling of 665823643 in words is "six hundred sixty-five million, eight hundred twenty-three thousand, six hundred forty-three".