643705 has 8 divisors (see below), whose sum is σ = 817992. Its totient is φ = 484608.

The previous prime is 643703. The next prime is 643723. The reversal of 643705 is 507346.

It can be written as a sum of positive squares in 4 ways, for example, as 356409 + 287296 = 597^2 + 536^2 .

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 643705 - 2¹ = 643703 is a prime.

It is a super-2 number, since 2×643705² = 828712254050, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 643705.

It is not an unprimeable number, because it can be changed into a prime (643703) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3702 + ... + 3871.

It is an arithmetic number, because the mean of its divisors is an integer number (102249).

2⁶⁴³⁷⁰⁵ is an apocalyptic number.

It is an amenable number.

643705 is a deficient number, since it is larger than the sum of its proper divisors (174287).

643705 is a wasteful number, since it uses less digits than its factorization.

643705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7595.

The product of its (nonzero) digits is 2520, while the sum is 25.

The square root of 643705 is about 802.3122833411. The cubic root of 643705 is about 86.3433631588.

The spelling of 643705 in words is "six hundred forty-three thousand, seven hundred five".