81649665751 has 16 divisors (see below), whose sum is σ = 88732200960. Its totient is φ = 74867548320.

The previous prime is 81649665737. The next prime is 81649665761. The reversal of 81649665751 is 15756694618.

It is not a de Polignac number, because 81649665751 - 2¹¹ = 81649663703 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81649665761) by changing a digit.

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, 169771 + ... + 438316.

It is an arithmetic number, because the mean of its divisors is an integer number (5545762560).

Almost surely, 2^81649665751 is an apocalyptic number.

81649665751 is a deficient number, since it is larger than the sum of its proper divisors (7082535209).

81649665751 is a wasteful number, since it uses less digits than its factorization.

81649665751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 608334.

The product of its digits is 10886400, while the sum is 58.

The spelling of 81649665751 in words is "eighty-one billion, six hundred forty-nine million, six hundred sixty-five thousand, seven hundred fifty-one".