1781817844991 has 2 divisors, whose sum is σ = 1781817844992. Its totient is φ = 1781817844990.

The previous prime is 1781817844981. The next prime is 1781817845033. The reversal of 1781817844991 is 1994487181871.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1781817844991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1781817844921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 890908922495 + 890908922496.

It is an arithmetic number, because the mean of its divisors is an integer number (890908922496).

Almost surely, 2^{1781817844991} is an apocalyptic number.

1781817844991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1781817844991 is an equidigital number, since it uses as much as digits as its factorization.

1781817844991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 32514048, while the sum is 68.

The spelling of 1781817844991 in words is "one trillion, seven hundred eighty-one billion, eight hundred seventeen million, eight hundred forty-four thousand, nine hundred ninety-one".