81317523456 has 416 divisors, whose sum is σ = 261786981120. Its totient is φ = 24795611136.

The previous prime is 81317523439. The next prime is 81317523481. The reversal of 81317523456 is 65432571318.

It is a happy number.

81317523456 is a `hidden beast` number, since 8 + 1 + 3 + 175 + 23 + 456 = 666.

It is a tau number, because it is divible by the number of its divisors (416).

It is a super-2 number, since 2×81317523456² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 234344275 + ... + 234344621.

Almost surely, 2^81317523456 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81317523456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (130893490560).

81317523456 is an abundant number, since it is smaller than the sum of its proper divisors (180469457664).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81317523456 is a wasteful number, since it uses less digits than its factorization.

81317523456 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 556 (or 528 counting only the distinct ones).

The product of its digits is 604800, while the sum is 45.

The spelling of 81317523456 in words is "eighty-one billion, three hundred seventeen million, five hundred twenty-three thousand, four hundred fifty-six".