81155756805200 has 720 divisors, whose sum is σ = 249384161142144. Its totient is φ = 25095987302400.

The previous prime is 81155756805181. The next prime is 81155756805203. The reversal of 81155756805200 is 250865755118.

It is a happy number.

It is a Cunningham number, because it is equal to 9008649²-1.

It is a super-2 number, since 2×81155756805200² (a number of 29 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81155756805203) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 22071185762 + ... + 22071189438.

Almost surely, 2^{81155756805200} is an apocalyptic number.

81155756805200 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 81155756805200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (124692080571072).

81155756805200 is an abundant number, since it is smaller than the sum of its proper divisors (168228404336944).

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

81155756805200 is a wasteful number, since it uses less digits than its factorization.

81155756805200 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4500 (or 4482 counting only the distinct ones).

The product of its (nonzero) digits is 3360000, while the sum is 53.

The spelling of 81155756805200 in words is "eighty-one trillion, one hundred fifty-five billion, seven hundred fifty-six million, eight hundred five thousand, two hundred".