643565 has 8 divisors (see below), whose sum is σ = 831768. Its totient is φ = 475200.

The previous prime is 643553. The next prime is 643567. The reversal of 643565 is 565346.

It can be written as a sum of positive squares in 4 ways, for example, as 106276 + 537289 = 326^2 + 733^2 .

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

It is not a de Polignac number, because 643565 - 2¹⁶ = 578029 is a prime.

It is a d-powerful number, because it can be written as 6⁷ + 4⁴ + 5⁵ + 3⁷ + 6⁷ + 5⁷ .

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643565.

It is not an unprimeable number, because it can be changed into a prime (643567) 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, 4886 + ... + 5015.

It is an arithmetic number, because the mean of its divisors is an integer number (103971).

2⁶⁴³⁵⁶⁵ is an apocalyptic number.

643565 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

643565 is a deficient number, since it is larger than the sum of its proper divisors (188203).

643565 is a wasteful number, since it uses less digits than its factorization.

643565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9919.

The product of its digits is 10800, while the sum is 29.

The square root of 643565 is about 802.2250307738. The cubic root of 643565 is about 86.3371030721.

The spelling of 643565 in words is "six hundred forty-three thousand, five hundred sixty-five".