1643605 has 4 divisors (see below), whose sum is σ = 1972332. Its totient is φ = 1314880.

The previous prime is 1643599. The next prime is 1643617. The reversal of 1643605 is 5063461.

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 580644 + 1062961 = 762^2 + 1031^2 .

It is not a de Polignac number, because 1643605 - 2³ = 1643597 is a prime.

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 1643605.

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, 164356 + ... + 164365.

It is an arithmetic number, because the mean of its divisors is an integer number (493083).

2^1643605 is an apocalyptic number.

It is an amenable number.

1643605 is a deficient number, since it is larger than the sum of its proper divisors (328727).

1643605 is an equidigital number, since it uses as much as digits as its factorization.

1643605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328726.

The product of its (nonzero) digits is 2160, while the sum is 25.

The square root of 1643605 is about 1282.0315908744. The cubic root of 1643605 is about 118.0137157283.

The spelling of 1643605 in words is "one million, six hundred forty-three thousand, six hundred five".