81990694126138 has 32 divisors (see below), whose sum is σ = 143982024912000. Its totient is φ = 35002141719552.

The previous prime is 81990694126129. The next prime is 81990694126151. The reversal of 81990694126138 is 83162149609918.

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, 232352808 + ... + 232705411.

It is an arithmetic number, because the mean of its divisors is an integer number (4499438278500).

Almost surely, 2^{81990694126138} is an apocalyptic number.

81990694126138 is a deficient number, since it is larger than the sum of its proper divisors (61991330785862).

81990694126138 is a wasteful number, since it uses less digits than its factorization.

81990694126138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 465058499 (or 465058485 counting only the distinct ones).

The product of its (nonzero) digits is 40310784, while the sum is 67.

The spelling of 81990694126138 in words is "eighty-one trillion, nine hundred ninety billion, six hundred ninety-four million, one hundred twenty-six thousand, one hundred thirty-eight".