81768961 has 2 divisors, whose sum is σ = 81768962. Its totient is φ = 81768960.

The previous prime is 81768959. The next prime is 81768977. The reversal of 81768961 is 16986718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 49914225 + 31854736 = 7065^2 + 5644^2 .

It is a cyclic number.

It is not a de Polignac number, because 81768961 - 2¹ = 81768959 is a prime.

Together with 81768959, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81768931) 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, 40884480 + 40884481.

It is an arithmetic number, because the mean of its divisors is an integer number (40884481).

Almost surely, 2^81768961 is an apocalyptic number.

It is an amenable number.

81768961 is a deficient number, since it is larger than the sum of its proper divisors (1).

81768961 is an equidigital number, since it uses as much as digits as its factorization.

81768961 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145152, while the sum is 46.

The square root of 81768961 is about 9042.6191449159. The cubic root of 81768961 is about 434.0397384808.

The spelling of 81768961 in words is "eighty-one million, seven hundred sixty-eight thousand, nine hundred sixty-one".