640521837789 has 8 divisors (see below), whose sum is σ = 855956949792. Its totient is φ = 426050642160.

The previous prime is 640521837763. The next prime is 640521837821. The reversal of 640521837789 is 987738125046.

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

It is a de Polignac number, because none of the positive numbers 2^k-640521837789 is a prime.

It is a Smith number, since the sum of its digits (60) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640521837289) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 240977542 + ... + 240980199.

It is an arithmetic number, because the mean of its divisors is an integer number (106994618724).

It is a 1-persistent number, because it is pandigital, but 2⋅640521837789 = 1281043675578 is not.

Almost surely, 2^640521837789 is an apocalyptic number.

It is an amenable number.

640521837789 is a deficient number, since it is larger than the sum of its proper divisors (215435112003).

640521837789 is a wasteful number, since it uses less digits than its factorization.

640521837789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 481958187.

The product of its (nonzero) digits is 20321280, while the sum is 60.

The spelling of 640521837789 in words is "six hundred forty billion, five hundred twenty-one million, eight hundred thirty-seven thousand, seven hundred eighty-nine".