81386506656 has 576 divisors, whose sum is σ = 312058656000. Its totient is φ = 19502235648.

The previous prime is 81386506609. The next prime is 81386506657. The reversal of 81386506656 is 65660568318.

81386506656 is a `hidden beast` number, since 8 + 1 + 3 + 86 + 506 + 6 + 56 = 666.

It is not an unprimeable number, because it can be changed into a prime (81386506657) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 12917395 + ... + 12923693.

It is an arithmetic number, because the mean of its divisors is an integer number (541768500).

Almost surely, 2^81386506656 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 81386506656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (156029328000).

81386506656 is an abundant number, since it is smaller than the sum of its proper divisors (230672149344).

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

81386506656 is a wasteful number, since it uses less digits than its factorization.

81386506656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6381 (or 6370 counting only the distinct ones).

The product of its (nonzero) digits is 6220800, while the sum is 54.

The spelling of 81386506656 in words is "eighty-one billion, three hundred eighty-six million, five hundred six thousand, six hundred fifty-six".