643245803866 has 4 divisors (see below), whose sum is σ = 964868705802. Its totient is φ = 321622901932.

The previous prime is 643245803861. The next prime is 643245803873. The reversal of 643245803866 is 668308542346.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 668308542346 = 2 ⋅334154271173.

It can be written as a sum of positive squares in only one way, i.e., 487035098641 + 156210705225 = 697879^2 + 395235^2 .

It is not an unprimeable number, because it can be changed into a prime (643245803861) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160811450965 + ... + 160811450968.

Almost surely, 2^643245803866 is an apocalyptic number.

643245803866 is a deficient number, since it is larger than the sum of its proper divisors (321622901936).

643245803866 is a wasteful number, since it uses less digits than its factorization.

643245803866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 321622901935.

The product of its (nonzero) digits is 19906560, while the sum is 55.

The spelling of 643245803866 in words is "six hundred forty-three billion, two hundred forty-five million, eight hundred three thousand, eight hundred sixty-six".