1981289 has 4 divisors (see below), whose sum is σ = 2067456. Its totient is φ = 1895124.

The previous prime is 1981277. The next prime is 1981297. The reversal of 1981289 is 9821891.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 9821891 = 163 ⋅60257.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981289 is a prime.

It is a super-3 number, since 3×1981289³ = 23332686175129321707, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1981589) 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, 43049 + ... + 43094.

It is an arithmetic number, because the mean of its divisors is an integer number (516864).

2^1981289 is an apocalyptic number.

It is an amenable number.

1981289 is a deficient number, since it is larger than the sum of its proper divisors (86167).

1981289 is an equidigital number, since it uses as much as digits as its factorization.

1981289 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 86166.

The product of its digits is 10368, while the sum is 38.

The square root of 1981289 is about 1407.5826796320. The cubic root of 1981289 is about 125.5979669232.

The spelling of 1981289 in words is "one million, nine hundred eighty-one thousand, two hundred eighty-nine".