1998805 has 4 divisors (see below), whose sum is σ = 2398572. Its totient is φ = 1599040.

The previous prime is 1998793. The next prime is 1998817. The reversal of 1998805 is 5088991.

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

It is an interprime number because it is at equal distance from previous prime (1998793) and next prime (1998817).

It can be written as a sum of positive squares in 2 ways, for example, as 1493284 + 505521 = 1222^2 + 711^2 .

It is a de Polignac number, because none of the positive numbers 2^k-1998805 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

1998805 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, 199876 + ... + 199885.

It is an arithmetic number, because the mean of its divisors is an integer number (599643).

2^1998805 is an apocalyptic number.

It is an amenable number.

1998805 is a deficient number, since it is larger than the sum of its proper divisors (399767).

1998805 is an equidigital number, since it uses as much as digits as its factorization.

1998805 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399766.

The product of its (nonzero) digits is 25920, while the sum is 40.

The square root of 1998805 is about 1413.7910029421. The cubic root of 1998805 is about 125.9670065625.

The spelling of 1998805 in words is "one million, nine hundred ninety-eight thousand, eight hundred five".