81909157104 has 240 divisors, whose sum is σ = 247007752992. Its totient is φ = 25245499392.

The previous prime is 81909157013. The next prime is 81909157129. The reversal of 81909157104 is 40175190918.

It is a happy number.

It is a super-2 number, since 2×81909157104² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81909157104.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 54861382 + ... + 54862874.

Almost surely, 2^81909157104 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81909157104, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (123503876496).

81909157104 is an abundant number, since it is smaller than the sum of its proper divisors (165098595888).

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

81909157104 is a wasteful number, since it uses less digits than its factorization.

81909157104 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1904 (or 1895 counting only the distinct ones).

The product of its (nonzero) digits is 90720, while the sum is 45.

The spelling of 81909157104 in words is "eighty-one billion, nine hundred nine million, one hundred fifty-seven thousand, one hundred four".