1981305 has 12 divisors (see below), whose sum is σ = 3434340. Its totient is φ = 1056672.

The previous prime is 1981297. The next prime is 1981337. The reversal of 1981305 is 5031891.

It can be written as a sum of positive squares in 2 ways, for example, as 423801 + 1557504 = 651^2 + 1248^2 .

It is not a de Polignac number, because 1981305 - 2³ = 1981297 is a prime.

It is a super-3 number, since 3×1981305³ = 23333251452572842875, which contains 333 as substring.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 21970 + ... + 22059.

It is an arithmetic number, because the mean of its divisors is an integer number (286195).

2^1981305 is an apocalyptic number.

1981305 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1981305 is a deficient number, since it is larger than the sum of its proper divisors (1453035).

1981305 is a wasteful number, since it uses less digits than its factorization.

1981305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44040 (or 44037 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 27.

The square root of 1981305 is about 1407.5883631233. The cubic root of 1981305 is about 125.5983050132.

It can be divided in two parts, 198130 and 5, that added together give a triangular number (198135 = T₆₂₉).

The spelling of 1981305 in words is "one million, nine hundred eighty-one thousand, three hundred five".