81329768647 has 2 divisors, whose sum is σ = 81329768648. Its totient is φ = 81329768646.

The previous prime is 81329768609. The next prime is 81329768671. The reversal of 81329768647 is 74686792318.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81329768647 - 2⁷ = 81329768519 is a prime.

It is a super-2 number, since 2×81329768647² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81329768347) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40664884323 + 40664884324.

It is an arithmetic number, because the mean of its divisors is an integer number (40664884324).

Almost surely, 2^81329768647 is an apocalyptic number.

81329768647 is a deficient number, since it is larger than the sum of its proper divisors (1).

81329768647 is an equidigital number, since it uses as much as digits as its factorization.

81329768647 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24385536, while the sum is 61.

It can be divided in two parts, 8132 and 9768647, that added together give a palindrome (9776779).

The spelling of 81329768647 in words is "eighty-one billion, three hundred twenty-nine million, seven hundred sixty-eight thousand, six hundred forty-seven".