643854331649 has 8 divisors (see below), whose sum is σ = 652322136960. Its totient is φ = 635394470256.

The previous prime is 643854331643. The next prime is 643854331741. The reversal of 643854331649 is 946133458346.

643854331649 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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-643854331649 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 643854331594 and 643854331603.

It is not an unprimeable number, because it can be changed into a prime (643854331643) 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, 1822727 + ... + 2147100.

It is an arithmetic number, because the mean of its divisors is an integer number (81540267120).

Almost surely, 2^643854331649 is an apocalyptic number.

It is an amenable number.

643854331649 is a deficient number, since it is larger than the sum of its proper divisors (8467805311).

643854331649 is a wasteful number, since it uses less digits than its factorization.

643854331649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3971959.

The product of its digits is 22394880, while the sum is 56.

The spelling of 643854331649 in words is "six hundred forty-three billion, eight hundred fifty-four million, three hundred thirty-one thousand, six hundred forty-nine".