81666318745 has 32 divisors (see below), whose sum is σ = 109487790720. Its totient is φ = 57963171840.

The previous prime is 81666318739. The next prime is 81666318763. The reversal of 81666318745 is 54781366618.

It is a de Polignac number, because none of the positive numbers 2^k-81666318745 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (55).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2892537 + ... + 2920633.

It is an arithmetic number, because the mean of its divisors is an integer number (3421493460).

Almost surely, 2^81666318745 is an apocalyptic number.

It is an amenable number.

81666318745 is a deficient number, since it is larger than the sum of its proper divisors (27821471975).

81666318745 is a wasteful number, since it uses less digits than its factorization.

81666318745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29385.

The product of its digits is 5806080, while the sum is 55.

The spelling of 81666318745 in words is "eighty-one billion, six hundred sixty-six million, three hundred eighteen thousand, seven hundred forty-five".