641605 has 4 divisors (see below), whose sum is σ = 769932. Its totient is φ = 513280.

The previous prime is 641581. The next prime is 641623. The reversal of 641605 is 506146.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 229441 + 412164 = 479^2 + 642^2 .

It is not a de Polignac number, because 641605 - 2⁹ = 641093 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a Duffinian number.

641605 is a lucky number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64156 + ... + 64165.

It is an arithmetic number, because the mean of its divisors is an integer number (192483).

2⁶⁴¹⁶⁰⁵ is an apocalyptic number.

It is an amenable number.

641605 is a deficient number, since it is larger than the sum of its proper divisors (128327).

641605 is a wasteful number, since it uses less digits than its factorization.

641605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128326.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 641605 is about 801.0024968750. The cubic root of 641605 is about 86.2493663750.

The spelling of 641605 in words is "six hundred forty-one thousand, six hundred five".