643681737 has 12 divisors (see below), whose sum is σ = 959755264. Its totient is φ = 415278360.

The previous prime is 643681729. The next prime is 643681741. The reversal of 643681737 is 737186346.

It is not a de Polignac number, because 643681737 - 2³ = 643681729 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 643681692 and 643681701.

It is not an unprimeable number, because it can be changed into a prime (643681757) 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 11 ways as a sum of consecutive naturals, for example, 1153273 + ... + 1153830.

Almost surely, 2^643681737 is an apocalyptic number.

It is an amenable number.

643681737 is a deficient number, since it is larger than the sum of its proper divisors (316073527).

643681737 is a wasteful number, since it uses less digits than its factorization.

643681737 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2307140 (or 2307137 counting only the distinct ones).

The product of its digits is 508032, while the sum is 45.

The square root of 643681737 is about 25370.8836464164. The cubic root of 643681737 is about 863.4232301885.

The spelling of 643681737 in words is "six hundred forty-three million, six hundred eighty-one thousand, seven hundred thirty-seven".