643984489345 has 4 divisors (see below), whose sum is σ = 772781387220. Its totient is φ = 515187591472.

The previous prime is 643984489259. The next prime is 643984489373. The reversal of 643984489345 is 543984489346.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 543984489346 = 2 ⋅271992244673.

It can be written as a sum of positive squares in 2 ways, for example, as 330111149809 + 313873339536 = 574553^2 + 560244^2 .

It is a cyclic number.

It is not a de Polignac number, because 643984489345 - 2²³ = 643976100737 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64398448930 + ... + 64398448939.

It is an arithmetic number, because the mean of its divisors is an integer number (193195346805).

Almost surely, 2^643984489345 is an apocalyptic number.

It is an amenable number.

643984489345 is a deficient number, since it is larger than the sum of its proper divisors (128796897875).

643984489345 is a wasteful number, since it uses less digits than its factorization.

643984489345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128796897874.

The product of its digits is 358318080, while the sum is 67.

Subtracting from 643984489345 its reverse (543984489346), we obtain a palindrome (99999999999).

The spelling of 643984489345 in words is "six hundred forty-three billion, nine hundred eighty-four million, four hundred eighty-nine thousand, three hundred forty-five".