81991740964 has 81 divisors (see below), whose sum is σ = 169337462931. Its totient is φ = 34635928320.

The previous prime is 81991740949. The next prime is 81991741033. The reversal of 81991740964 is 46904719918.

The square root of 81991740964 is 286342.

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

It can be written as a sum of positive squares in 4 ways, for example, as 77423062500 + 4568678464 = 278250^2 + 67592^2 .

It is a junction number, because it is equal to n+sod(n) for n = 81991740899 and 81991740908.

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 26 ways as a sum of consecutive naturals, for example, 452992954 + ... + 452993134.

Almost surely, 2^81991740964 is an apocalyptic number.

81991740964 is the 286342-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81991740964

81991740964 is an abundant number, since it is smaller than the sum of its proper divisors (87345721967).

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

81991740964 is a wasteful number, since it uses less digits than its factorization.

81991740964 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 606 (or 303 counting only the distinct ones).

The product of its (nonzero) digits is 3919104, while the sum is 58.

The spelling of 81991740964 in words is "eighty-one billion, nine hundred ninety-one million, seven hundred forty thousand, nine hundred sixty-four".