81171138390 has 64 divisors (see below), whose sum is σ = 205180770816. Its totient is φ = 20511003392.

The previous prime is 81171138379. The next prime is 81171138397. The reversal of 81171138390 is 9383117118.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81171138397) 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 31 ways as a sum of consecutive naturals, for example, 475887 + ... + 623546.

It is an arithmetic number, because the mean of its divisors is an integer number (3205949544).

Almost surely, 2^81171138390 is an apocalyptic number.

81171138390 is an abundant number, since it is smaller than the sum of its proper divisors (124009632426).

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

81171138390 is a wasteful number, since it uses less digits than its factorization.

81171138390 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1099573.

The product of its (nonzero) digits is 36288, while the sum is 42.

The spelling of 81171138390 in words is "eighty-one billion, one hundred seventy-one million, one hundred thirty-eight thousand, three hundred ninety".