1981559 has 4 divisors (see below), whose sum is σ = 1988616. Its totient is φ = 1974504.

The previous prime is 1981547. The next prime is 1981583. The reversal of 1981559 is 9551891.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9551891 = 43 ⋅222137.

It is a cyclic number.

It is not a de Polignac number, because 1981559 - 2⁴ = 1981543 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981589) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3089 + ... + 3674.

It is an arithmetic number, because the mean of its divisors is an integer number (497154).

2^1981559 is an apocalyptic number.

1981559 is a deficient number, since it is larger than the sum of its proper divisors (7057).

1981559 is an equidigital number, since it uses as much as digits as its factorization.

1981559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7056.

The product of its digits is 16200, while the sum is 38.

The square root of 1981559 is about 1407.6785854733. The cubic root of 1981559 is about 125.6036719483.

The spelling of 1981559 in words is "one million, nine hundred eighty-one thousand, five hundred fifty-nine".