81057517 has 4 divisors (see below), whose sum is σ = 81321856. Its totient is φ = 80793180.

The previous prime is 81057503. The next prime is 81057569. The reversal of 81057517 is 71575018.

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, and also an emirpimes, since its reverse is a distinct semiprime: 71575018 = 2 ⋅35787509.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81057517 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 (81057577) 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, 131709 + ... + 132322.

It is an arithmetic number, because the mean of its divisors is an integer number (20330464).

Almost surely, 2^81057517 is an apocalyptic number.

It is an amenable number.

81057517 is a deficient number, since it is larger than the sum of its proper divisors (264339).

81057517 is a wasteful number, since it uses less digits than its factorization.

81057517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 264338.

The product of its (nonzero) digits is 9800, while the sum is 34.

The square root of 81057517 is about 9003.1948218396. The cubic root of 81057517 is about 432.7772590447. Note that the first 3 decimals are identical.

The spelling of 81057517 in words is "eighty-one million, fifty-seven thousand, five hundred seventeen".