1981543 has 2 divisors, whose sum is σ = 1981544. Its totient is φ = 1981542.

The previous prime is 1981523. The next prime is 1981547. The reversal of 1981543 is 3451891.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1981543 is a prime.

It is an Ulam number.

1981543 is a lucky number.

It is a zygodrome in base 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1981547) 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 as a sum of consecutive naturals, namely, 990771 + 990772.

It is an arithmetic number, because the mean of its divisors is an integer number (990772).

2^1981543 is an apocalyptic number.

1981543 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981543 is an equidigital number, since it uses as much as digits as its factorization.

1981543 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 31.

The square root of 1981543 is about 1407.6729023463. The cubic root of 1981543 is about 125.6033338872.

The spelling of 1981543 in words is "one million, nine hundred eighty-one thousand, five hundred forty-three".