81863868646 has 32 divisors (see below), whose sum is σ = 140857475328. Its totient is φ = 34954809120.

The previous prime is 81863868641. The next prime is 81863868659. The reversal of 81863868646 is 64686836818.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81863868641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7979256 + ... + 7989508.

It is an arithmetic number, because the mean of its divisors is an integer number (4401796104).

Almost surely, 2^81863868646 is an apocalyptic number.

81863868646 is a deficient number, since it is larger than the sum of its proper divisors (58993606682).

81863868646 is a wasteful number, since it uses less digits than its factorization.

81863868646 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12316.

The product of its digits is 63700992, while the sum is 64.

The spelling of 81863868646 in words is "eighty-one billion, eight hundred sixty-three million, eight hundred sixty-eight thousand, six hundred forty-six".