81561845266 has 8 divisors (see below), whose sum is σ = 133464837744. Its totient is φ = 37073566020.

The previous prime is 81561845249. The next prime is 81561845303. The reversal of 81561845266 is 66254816518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×81561845266² (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 (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1853678280 + ... + 1853678323.

It is an arithmetic number, because the mean of its divisors is an integer number (16683104718).

Almost surely, 2^81561845266 is an apocalyptic number.

81561845266 is a deficient number, since it is larger than the sum of its proper divisors (51902992478).

81561845266 is a wasteful number, since it uses less digits than its factorization.

81561845266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3707356616.

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

The spelling of 81561845266 in words is "eighty-one billion, five hundred sixty-one million, eight hundred forty-five thousand, two hundred sixty-six".