81561416517 has 12 divisors (see below), whose sum is σ = 134641068640. Its totient is φ = 46606523688.

The previous prime is 81561416513. The next prime is 81561416617. The reversal of 81561416517 is 71561416518.

81561416517 is a `hidden beast` number, since 8 + 1 + 5 + 614 + 16 + 5 + 17 = 666.

It is not a de Polignac number, because 81561416517 - 2² = 81561416513 is a prime.

It is a super-2 number, since 2×81561416517² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81561416513) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 647312767 + ... + 647312892.

Almost surely, 2^81561416517 is an apocalyptic number.

It is an amenable number.

81561416517 is a deficient number, since it is larger than the sum of its proper divisors (53079652123).

81561416517 is a wasteful number, since it uses less digits than its factorization.

81561416517 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1294625672 (or 1294625669 counting only the distinct ones).

The product of its digits is 201600, while the sum is 45.

Subtracting from 81561416517 its reverse (71561416518), we obtain a palindrome (9999999999).

The spelling of 81561416517 in words is "eighty-one billion, five hundred sixty-one million, four hundred sixteen thousand, five hundred seventeen".