81315897394 has 32 divisors (see below), whose sum is σ = 129500559216. Its totient is φ = 38162227200.

The previous prime is 81315897367. The next prime is 81315897433. The reversal of 81315897394 is 49379851318.

It can be written as a sum of positive squares in 8 ways, for example, as 65247039225 + 16068858169 = 255435^2 + 126763^2 .

It is a super-2 number, since 2×81315897394² (a number of 23 digits) contains 22 as substring.

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 15 ways as a sum of consecutive naturals, for example, 29280534 + ... + 29283310.

Almost surely, 2^81315897394 is an apocalyptic number.

81315897394 is a deficient number, since it is larger than the sum of its proper divisors (48184661822).

81315897394 is a wasteful number, since it uses less digits than its factorization.

81315897394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4830.

The product of its digits is 6531840, while the sum is 58.

The spelling of 81315897394 in words is "eighty-one billion, three hundred fifteen million, eight hundred ninety-seven thousand, three hundred ninety-four".