81173730772 has 12 divisors (see below), whose sum is σ = 145518761556. Its totient is φ = 39596941760.

The previous prime is 81173730767. The next prime is 81173730773. The reversal of 81173730772 is 27703737118.

It can be written as a sum of positive squares in 2 ways, for example, as 12569548996 + 68604181776 = 112114^2 + 261924^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81173730773) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 247480723 + ... + 247481050.

It is an arithmetic number, because the mean of its divisors is an integer number (12126563463).

Almost surely, 2^81173730772 is an apocalyptic number.

81173730772 is a gapful number since it is divisible by the number (82) formed by its first and last digit.

It is an amenable number.

81173730772 is a deficient number, since it is larger than the sum of its proper divisors (64345030784).

81173730772 is a wasteful number, since it uses less digits than its factorization.

81173730772 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 494961818 (or 494961816 counting only the distinct ones).

The product of its (nonzero) digits is 345744, while the sum is 46.

The spelling of 81173730772 in words is "eighty-one billion, one hundred seventy-three million, seven hundred thirty thousand, seven hundred seventy-two".