1781881 has 2 divisors, whose sum is σ = 1781882. Its totient is φ = 1781880.

The previous prime is 1781873. The next prime is 1781893. The reversal of 1781881 is 1881871.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1648656 + 133225 = 1284^2 + 365^2 .

It is a cyclic number.

It is not a de Polignac number, because 1781881 - 2³ = 1781873 is a prime.

It is a super-2 number, since 2×1781881² = 6350199796322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1781831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 890940 + 890941.

It is an arithmetic number, because the mean of its divisors is an integer number (890941).

2^1781881 is an apocalyptic number.

It is an amenable number.

1781881 is a deficient number, since it is larger than the sum of its proper divisors (1).

1781881 is an equidigital number, since it uses as much as digits as its factorization.

1781881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3584, while the sum is 34.

The square root of 1781881 is about 1334.8711548311. The cubic root of 1781881 is about 121.2345018630.

It can be divided in two parts, 1781 and 881, that added together give a palindrome (2662).

The spelling of 1781881 in words is "one million, seven hundred eighty-one thousand, eight hundred eighty-one".