1981785 has 16 divisors (see below), whose sum is σ = 3415104. Its totient is φ = 975552.

The previous prime is 1981753. The next prime is 1981787. The reversal of 1981785 is 5871891.

It is not a de Polignac number, because 1981785 - 2⁵ = 1981753 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is not an unprimeable number, because it can be changed into a prime (1981787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4887 + ... + 5276.

It is an arithmetic number, because the mean of its divisors is an integer number (213444).

2^1981785 is an apocalyptic number.

1981785 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1981785 is a deficient number, since it is larger than the sum of its proper divisors (1433319).

1981785 is a wasteful number, since it uses less digits than its factorization.

1981785 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10184.

The product of its digits is 20160, while the sum is 39.

The square root of 1981785 is about 1407.7588571911. The cubic root of 1981785 is about 125.6084468672.

The spelling of 1981785 in words is "one million, nine hundred eighty-one thousand, seven hundred eighty-five".