81983778641 has 2 divisors, whose sum is σ = 81983778642. Its totient is φ = 81983778640.

The previous prime is 81983778577. The next prime is 81983778659. The reversal of 81983778641 is 14687738918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60979363600 + 21004415041 = 246940^2 + 144929^2 .

It is a cyclic number.

It is not a de Polignac number, because 81983778641 - 2⁶ = 81983778577 is a prime.

It is not a weakly prime, because it can be changed into another prime (81983778241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40991889320 + 40991889321.

It is an arithmetic number, because the mean of its divisors is an integer number (40991889321).

Almost surely, 2^81983778641 is an apocalyptic number.

It is an amenable number.

81983778641 is a deficient number, since it is larger than the sum of its proper divisors (1).

81983778641 is an equidigital number, since it uses as much as digits as its factorization.

81983778641 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16257024, while the sum is 62.

The spelling of 81983778641 in words is "eighty-one billion, nine hundred eighty-three million, seven hundred seventy-eight thousand, six hundred forty-one".