643542667 has 4 divisors (see below), whose sum is σ = 681398136. Its totient is φ = 605687200.

The previous prime is 643542643. The next prime is 643542689. The reversal of 643542667 is 766245346.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 643542667 - 2¹¹ = 643540619 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (643542607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18927709 + ... + 18927742.

It is an arithmetic number, because the mean of its divisors is an integer number (170349534).

Almost surely, 2^643542667 is an apocalyptic number.

643542667 is a deficient number, since it is larger than the sum of its proper divisors (37855469).

643542667 is a wasteful number, since it uses less digits than its factorization.

643542667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 37855468.

The product of its digits is 725760, while the sum is 43.

The square root of 643542667 is about 25368.1427581918. The cubic root of 643542667 is about 863.3610437018.

The spelling of 643542667 in words is "six hundred forty-three million, five hundred forty-two thousand, six hundred sixty-seven".