1981563 has 4 divisors (see below), whose sum is σ = 2642088. Its totient is φ = 1321040.

The previous prime is 1981547. The next prime is 1981583. The reversal of 1981563 is 3651891.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 3651891 = 3 ⋅1217297.

It is a cyclic number.

It is not a de Polignac number, because 1981563 - 2⁴ = 1981547 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (1981513) 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, 330258 + ... + 330263.

It is an arithmetic number, because the mean of its divisors is an integer number (660522).

2^1981563 is an apocalyptic number.

1981563 is a deficient number, since it is larger than the sum of its proper divisors (660525).

1981563 is an equidigital number, since it uses as much as digits as its factorization.

1981563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 660524.

The product of its digits is 6480, while the sum is 33.

The square root of 1981563 is about 1407.6800062514. The cubic root of 1981563 is about 125.6037564633.

The spelling of 1981563 in words is "one million, nine hundred eighty-one thousand, five hundred sixty-three".