81385517 has 4 divisors (see below), whose sum is σ = 81483360. Its totient is φ = 81287676.

The previous prime is 81385481. The next prime is 81385543. The reversal of 81385517 is 71558318.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81385517 - 2¹⁰ = 81384493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81085517) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47663 + ... + 49340.

It is an arithmetic number, because the mean of its divisors is an integer number (20370840).

Almost surely, 2^81385517 is an apocalyptic number.

It is an amenable number.

81385517 is a deficient number, since it is larger than the sum of its proper divisors (97843).

81385517 is an equidigital number, since it uses as much as digits as its factorization.

81385517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97842.

The product of its digits is 33600, while the sum is 38.

The square root of 81385517 is about 9021.3921874620. The cubic root of 81385517 is about 433.3602191734.

The spelling of 81385517 in words is "eighty-one million, three hundred eighty-five thousand, five hundred seventeen".