81331806240 has 384 divisors, whose sum is σ = 290873721600. Its totient is φ = 21220392960.

The previous prime is 81331806223. The next prime is 81331806251. The reversal of 81331806240 is 4260813318.

81331806240 is a `hidden beast` number, since 8 + 1 + 331 + 80 + 6 + 240 = 666.

It is a super-2 number, since 2×81331806240² (a number of 23 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 81331806195 and 81331806204.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 39082000 + ... + 39084080.

It is an arithmetic number, because the mean of its divisors is an integer number (757483650).

Almost surely, 2^81331806240 is an apocalyptic number.

81331806240 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81331806240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (145436860800).

81331806240 is an abundant number, since it is smaller than the sum of its proper divisors (209541915360).

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

81331806240 is a wasteful number, since it uses less digits than its factorization.

81331806240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2297 (or 2283 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The spelling of 81331806240 in words is "eighty-one billion, three hundred thirty-one million, eight hundred six thousand, two hundred forty".