1981786 has 4 divisors (see below), whose sum is σ = 2972682. Its totient is φ = 990892.

The previous prime is 1981753. The next prime is 1981787. The reversal of 1981786 is 6871891.

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

It can be written as a sum of positive squares in only one way, i.e., 1311025 + 670761 = 1145^2 + 819^2 .

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 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 as a sum of consecutive naturals, namely, 495445 + ... + 495448.

2^1981786 is an apocalyptic number.

1981786 is a deficient number, since it is larger than the sum of its proper divisors (990896).

1981786 is an equidigital number, since it uses as much as digits as its factorization.

1981786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 990895.

The product of its digits is 24192, while the sum is 40.

The square root of 1981786 is about 1407.7592123655. The cubic root of 1981786 is about 125.6084679944.

The spelling of 1981786 in words is "one million, nine hundred eighty-one thousand, seven hundred eighty-six".