643749943 has 4 divisors (see below), whose sum is σ = 643804408. Its totient is φ = 643695480.

The previous prime is 643749941. The next prime is 643749959. The reversal of 643749943 is 349947346.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 643749943 - 2¹ = 643749941 is a prime.

It is a super-2 number, since 2×643749943² = 828827978225006498, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643749941) 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, 1221 + ... + 35902.

It is an arithmetic number, because the mean of its divisors is an integer number (160951102).

Almost surely, 2^643749943 is an apocalyptic number.

643749943 is a deficient number, since it is larger than the sum of its proper divisors (54465).

643749943 is a wasteful number, since it uses less digits than its factorization.

643749943 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54464.

The product of its digits is 1959552, while the sum is 49.

The square root of 643749943 is about 25372.2277894551. The cubic root of 643749943 is about 863.4537258830.

The spelling of 643749943 in words is "six hundred forty-three million, seven hundred forty-nine thousand, nine hundred forty-three".