81812016784 has 45 divisors (see below), whose sum is σ = 165755512713. Its totient is φ = 39114901056.

The previous prime is 81812016779. The next prime is 81812016787. The reversal of 81812016784 is 48761021818.

The square root of 81812016784 is 286028.

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

It can be written as a sum of positive squares in only one way, i.e., 14502903184 + 67309113600 = 120428^2 + 259440^2 .

It is a Harshad number since it is a multiple of its sum of digits (46).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81812016787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 26313022 + ... + 26316130.

Almost surely, 2^81812016784 is an apocalyptic number.

81812016784 is the 286028-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81812016784

81812016784 is an abundant number, since it is smaller than the sum of its proper divisors (83943495929).

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

81812016784 is an frugal number, since it uses more digits than its factorization.

81812016784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6272 (or 3134 counting only the distinct ones).

The product of its (nonzero) digits is 172032, while the sum is 46.

The spelling of 81812016784 in words is "eighty-one billion, eight hundred twelve million, sixteen thousand, seven hundred eighty-four".