643205 has 8 divisors (see below), whose sum is σ = 776952. Its totient is φ = 511168.

The previous prime is 643199. The next prime is 643213. The reversal of 643205 is 502346.

It is a Cunningham number, because it is equal to 802²+1.

It can be written as a sum of positive squares in 4 ways, for example, as 148996 + 494209 = 386^2 + 703^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 643205 - 2¹⁸ = 381061 is a prime.

It is a Duffinian 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 643205.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 659 + ... + 1311.

It is an arithmetic number, because the mean of its divisors is an integer number (97119).

2⁶⁴³²⁰⁵ is an apocalyptic number.

It is an amenable number.

643205 is a deficient number, since it is larger than the sum of its proper divisors (133747).

643205 is a wasteful number, since it uses less digits than its factorization.

643205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 855.

The product of its (nonzero) digits is 720, while the sum is 20.

The square root of 643205 is about 802.0006234412. Note that the first 3 decimals coincide. The cubic root of 643205 is about 86.3210015365.

It can be divided in two parts, 643 and 205, that added together give a palindrome (848).

The spelling of 643205 in words is "six hundred forty-three thousand, two hundred five".