81218465538 has 32 divisors (see below), whose sum is σ = 185930981376. Its totient is φ = 23169179088.

The previous prime is 81218465509. The next prime is 81218465543. The reversal of 81218465538 is 83556481218.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1476706 + ... + 1530717.

It is an arithmetic number, because the mean of its divisors is an integer number (5810343168).

Almost surely, 2^81218465538 is an apocalyptic number.

81218465538 is an abundant number, since it is smaller than the sum of its proper divisors (104712515838).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81218465538 is a wasteful number, since it uses less digits than its factorization.

81218465538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3008078.

The product of its digits is 1843200, while the sum is 51.

The spelling of 81218465538 in words is "eighty-one billion, two hundred eighteen million, four hundred sixty-five thousand, five hundred thirty-eight".