1981861 has 8 divisors (see below), whose sum is σ = 2338304.
Its totient is φ = 1643760.
The previous prime is 1981853. The next prime is 1981867. The reversal of 1981861 is 1681891.
It is a sphenic number, since it is the product of 3 distinct primes.
It is a cyclic number.
It is not a de Polignac number, because 1981861 - 23 = 1981853 is a prime.
1981861 is a strobogrammatic number because it is the same when read upside-down.
It is a Duffinian number.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (1981867) 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 7 ways as a sum of consecutive naturals, for example, 4350 + ... + 4783.
It is an arithmetic number, because the mean of its divisors is an integer number (292288).
21981861 is an apocalyptic number.
It is an amenable number.
1981861 is a deficient number, since it is larger than the sum of its proper divisors (356443).
1981861 is an equidigital number, since it uses as much as digits as its factorization.
1981861 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 9171.
The product of its digits is 3456, while the sum is 34.
The square root of 1981861 is about 1407.7858501917.
The cubic root of 1981861 is about 125.6100525106.
The spelling of 1981861 in words is "one million, nine hundred eighty-one thousand, eight hundred sixty-one".