643967699 has 4 divisors (see below), whose sum is σ = 658943736. Its totient is φ = 628991664.

The previous prime is 643967683. The next prime is 643967729. The reversal of 643967699 is 996769346.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 996769346 = 2 ⋅498384673.

It is a cyclic number.

It is not a de Polignac number, because 643967699 - 2⁴ = 643967683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643967609) 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, 7487954 + ... + 7488039.

It is an arithmetic number, because the mean of its divisors is an integer number (164735934).

Almost surely, 2^643967699 is an apocalyptic number.

643967699 is a deficient number, since it is larger than the sum of its proper divisors (14976037).

643967699 is a wasteful number, since it uses less digits than its factorization.

643967699 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14976036.

The product of its digits is 13226976, while the sum is 59.

The square root of 643967699 is about 25376.5186540629. The cubic root of 643967699 is about 863.5510727050.

The spelling of 643967699 in words is "six hundred forty-three million, nine hundred sixty-seven thousand, six hundred ninety-nine".