81216320500 has 192 divisors, whose sum is σ = 205865307648. Its totient is φ = 27416524800.

The previous prime is 81216320447. The next prime is 81216320509. The reversal of 81216320500 is 502361218.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81216320509) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 68420907 + ... + 68422093.

It is an arithmetic number, because the mean of its divisors is an integer number (1072215144).

Almost surely, 2^81216320500 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 81216320500, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (102932653824).

81216320500 is an abundant number, since it is smaller than the sum of its proper divisors (124648987148).

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

81216320500 is a wasteful number, since it uses less digits than its factorization.

81216320500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1499 (or 1487 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 28.

Adding to 81216320500 its reverse (502361218), we get a palindrome (81718681718).

The spelling of 81216320500 in words is "eighty-one billion, two hundred sixteen million, three hundred twenty thousand, five hundred".