641891609856 has 720 divisors, whose sum is σ = 2269579568256. Its totient is φ = 176614981632.

The previous prime is 641891609747. The next prime is 641891609911. The reversal of 641891609856 is 658906198146.

641891609856 is a `hidden beast` number, since 6 + 4 + 18 + 9 + 1 + 609 + 8 + 5 + 6 = 666.

It is a Smith number, since the sum of its digits (63) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a junction number, because it is equal to n+sod(n) for n = 641891609793 and 641891609802.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 574656210 + ... + 574657326.

Almost surely, 2^641891609856 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 641891609856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1134789784128).

641891609856 is an abundant number, since it is smaller than the sum of its proper divisors (1627687958400).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

641891609856 is a wasteful number, since it uses less digits than its factorization.

641891609856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1296 (or 1273 counting only the distinct ones).

The product of its (nonzero) digits is 22394880, while the sum is 63.

The spelling of 641891609856 in words is "six hundred forty-one billion, eight hundred ninety-one million, six hundred nine thousand, eight hundred fifty-six".