1981139 has 4 divisors (see below), whose sum is σ = 2027256. Its totient is φ = 1935024.

The previous prime is 1981099. The next prime is 1981141. The reversal of 1981139 is 9311891.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9311891 = 367 ⋅25373.

It is a cyclic number.

It is not a de Polignac number, because 1981139 - 2²⁰ = 932563 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981159) 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 3 ways as a sum of consecutive naturals, for example, 22994 + ... + 23079.

It is an arithmetic number, because the mean of its divisors is an integer number (506814).

2^1981139 is an apocalyptic number.

1981139 is a deficient number, since it is larger than the sum of its proper divisors (46117).

1981139 is an equidigital number, since it uses as much as digits as its factorization.

1981139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 46116.

The product of its digits is 1944, while the sum is 32.

The square root of 1981139 is about 1407.5293957854. The cubic root of 1981139 is about 125.5947972408.

It can be divided in two parts, 198 and 1139, that multiplied together give a palindrome (225522).

The spelling of 1981139 in words is "one million, nine hundred eighty-one thousand, one hundred thirty-nine".