81505682064 has 135 divisors (see below), whose sum is σ = 234799426953. Its totient is φ = 26393164416.

The previous prime is 81505682057. The next prime is 81505682077. The reversal of 81505682064 is 46028650518.

The square root of 81505682064 is 285492.

It is a perfect power (a square), and thus also a powerful number.

81505682064 is a `hidden beast` number, since 8 + 1 + 5 + 0 + 568 + 20 + 64 = 666.

It can be written as a sum of positive squares in only one way, i.e., 72932403600 + 8573278464 = 270060^2 + 92592^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 126758127 + ... + 126758769.

Almost surely, 2^81505682064 is an apocalyptic number.

81505682064 is the 285492-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81505682064

81505682064 is an abundant number, since it is smaller than the sum of its proper divisors (153293744889).

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

81505682064 is an equidigital number, since it uses as much as digits as its factorization.

81505682064 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1374 (or 685 counting only the distinct ones).

The product of its (nonzero) digits is 460800, while the sum is 45.

The spelling of 81505682064 in words is "eighty-one billion, five hundred five million, six hundred eighty-two thousand, sixty-four".