81729313 has 2 divisors, whose sum is σ = 81729314. Its totient is φ = 81729312.

The previous prime is 81729311. The next prime is 81729343. The reversal of 81729313 is 31392718.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 41177889 + 40551424 = 6417^2 + 6368^2 .

It is a cyclic number.

It is not a de Polignac number, because 81729313 - 2¹ = 81729311 is a prime.

Together with 81729311, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81729311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40864656 + 40864657.

It is an arithmetic number, because the mean of its divisors is an integer number (40864657).

Almost surely, 2^81729313 is an apocalyptic number.

It is an amenable number.

81729313 is a deficient number, since it is larger than the sum of its proper divisors (1).

81729313 is an equidigital number, since it uses as much as digits as its factorization.

81729313 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 34.

The square root of 81729313 is about 9040.4265939169. The cubic root of 81729313 is about 433.9695749800.

The spelling of 81729313 in words is "eighty-one million, seven hundred twenty-nine thousand, three hundred thirteen".