81356517 has 24 divisors (see below), whose sum is σ = 129755808. Its totient is φ = 48708000.

The previous prime is 81356503. The next prime is 81356531. The reversal of 81356517 is 71565318.

81356517 is a `hidden beast` number, since 8 + 135 + 6 + 517 = 666.

It is an interprime number because it is at equal distance from previous prime (81356503) and next prime (81356531).

It is not a de Polignac number, because 81356517 - 2⁴ = 81356501 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81356567) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3267 + ... + 13167.

It is an arithmetic number, because the mean of its divisors is an integer number (5406492).

Almost surely, 2^81356517 is an apocalyptic number.

It is an amenable number.

81356517 is a deficient number, since it is larger than the sum of its proper divisors (48399291).

81356517 is a wasteful number, since it uses less digits than its factorization.

81356517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10001 (or 9998 counting only the distinct ones).

The product of its digits is 25200, while the sum is 36.

The square root of 81356517 is about 9019.7847535293. The cubic root of 81356517 is about 433.3087401559.

The spelling of 81356517 in words is "eighty-one million, three hundred fifty-six thousand, five hundred seventeen".