1981989 has 10 divisors (see below), whose sum is σ = 2960870. Its totient is φ = 1321272.

The previous prime is 1981963. The next prime is 1981997. The reversal of 1981989 is 9891891.

It can be written as a sum of positive squares in only one way, i.e., 1368900 + 613089 = 1170^2 + 783^2 .

It is not a de Polignac number, because 1981989 - 2⁹ = 1981477 is a prime.

It is a super-2 number, since 2×1981989² = 7856560792242, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981919) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 12154 + ... + 12315.

It is an arithmetic number, because the mean of its divisors is an integer number (296087).

2^1981989 is an apocalyptic number.

It is an amenable number.

1981989 is a deficient number, since it is larger than the sum of its proper divisors (978881).

1981989 is an equidigital number, since it uses as much as digits as its factorization.

1981989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24481 (or 24472 counting only the distinct ones).

The product of its digits is 46656, while the sum is 45.

The square root of 1981989 is about 1407.8313109176. The cubic root of 1981989 is about 125.6127566593.

It can be divided in two parts, 198 and 1989, that added together give a 7-th power (2187 = 3⁷).

The spelling of 1981989 in words is "one million, nine hundred eighty-one thousand, nine hundred eighty-nine".