643890647 has 8 divisors (see below), whose sum is σ = 659848896. Its totient is φ = 628026592.

The previous prime is 643890641. The next prime is 643890649. The reversal of 643890647 is 746098346.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643890647 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (47).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643890641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9608 + ... + 37149.

It is an arithmetic number, because the mean of its divisors is an integer number (82481112).

Almost surely, 2^643890647 is an apocalyptic number.

643890647 is a deficient number, since it is larger than the sum of its proper divisors (15958249).

643890647 is a wasteful number, since it uses less digits than its factorization.

643890647 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47097.

The product of its (nonzero) digits is 870912, while the sum is 47.

The square root of 643890647 is about 25375.0004334975. Note that the first 3 decimals coincide. The cubic root of 643890647 is about 863.5166294705.

The spelling of 643890647 in words is "six hundred forty-three million, eight hundred ninety thousand, six hundred forty-seven".