641666560 has 80 divisors (see below), whose sum is σ = 1571524416. Its totient is φ = 251158528.

The previous prime is 641666453. The next prime is 641666561. The reversal of 641666560 is 65666146.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (641666561) 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, 117654 + ... + 122986.

Almost surely, 2^641666560 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 641666560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (785762208).

641666560 is an abundant number, since it is smaller than the sum of its proper divisors (929857856).

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

641666560 is an equidigital number, since it uses as much as digits as its factorization.

641666560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5403 (or 5387 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 40.

The square root of 641666560 is about 25331.1381505056. The cubic root of 641666560 is about 862.5212473937.

The spelling of 641666560 in words is "six hundred forty-one million, six hundred sixty-six thousand, five hundred sixty".