81542856661 has 16 divisors (see below), whose sum is σ = 97415741440. Its totient is φ = 66783029040.

The previous prime is 81542856631. The next prime is 81542856767. The reversal of 81542856661 is 16665824518.

It is a de Polignac number, because none of the positive numbers 2^k-81542856661 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 81542856599 and 81542856608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81542856631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2361171 + ... + 2395456.

It is an arithmetic number, because the mean of its divisors is an integer number (6088483840).

Almost surely, 2^81542856661 is an apocalyptic number.

It is an amenable number.

81542856661 is a deficient number, since it is larger than the sum of its proper divisors (15872884779).

81542856661 is a wasteful number, since it uses less digits than its factorization.

81542856661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4756744.

The product of its digits is 2764800, while the sum is 52.

The spelling of 81542856661 in words is "eighty-one billion, five hundred forty-two million, eight hundred fifty-six thousand, six hundred sixty-one".