641680 has 40 divisors (see below), whose sum is σ = 1609272. Its totient is φ = 236544.

The previous prime is 641639. The next prime is 641681. The reversal of 641680 is 86146.

641680 = T₂₇ + T₂₈ + ... + T₁₅₆.

It can be written as a sum of positive squares in 4 ways, for example, as 20736 + 620944 = 144^2 + 788^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (641681) 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, 732 + ... + 1348.

2⁶⁴¹⁶⁸⁰ 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 641680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (804636).

641680 is an abundant number, since it is smaller than the sum of its proper divisors (967592).

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

641680 is a wasteful number, since it uses less digits than its factorization.

641680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 643 (or 637 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 641680 is about 801.0493118404. The cubic root of 641680 is about 86.2527269319.

The spelling of 641680 in words is "six hundred forty-one thousand, six hundred eighty".