81513241 has 2 divisors, whose sum is σ = 81513242. Its totient is φ = 81513240.

The previous prime is 81513239. The next prime is 81513259. The reversal of 81513241 is 14231518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80928016 + 585225 = 8996^2 + 765^2 .

It is a cyclic number.

It is not a de Polignac number, because 81513241 - 2¹ = 81513239 is a prime.

Together with 81513239, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81513941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40756620 + 40756621.

It is an arithmetic number, because the mean of its divisors is an integer number (40756621).

Almost surely, 2^81513241 is an apocalyptic number.

It is an amenable number.

81513241 is a deficient number, since it is larger than the sum of its proper divisors (1).

81513241 is an equidigital number, since it uses as much as digits as its factorization.

81513241 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 960, while the sum is 25.

The square root of 81513241 is about 9028.4683640139. The cubic root of 81513241 is about 433.5868015464.

Adding to 81513241 its reverse (14231518), we get a palindrome (95744759).

The spelling of 81513241 in words is "eighty-one million, five hundred thirteen thousand, two hundred forty-one".