81225918720 has 432 divisors, whose sum is σ = 294148213632. Its totient is φ = 21459271680.

The previous prime is 81225918691. The next prime is 81225918793. The reversal of 81225918720 is 2781952218.

It is a tau number, because it is divible by the number of its divisors (432).

It is a Harshad number since it is a multiple of its sum of digits (45).

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, 35146365 + ... + 35148675.

Almost surely, 2^81225918720 is an apocalyptic number.

81225918720 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 81225918720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147074106816).

81225918720 is an abundant number, since it is smaller than the sum of its proper divisors (212922294912).

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

81225918720 is a wasteful number, since it uses less digits than its factorization.

81225918720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2460 (or 2434 counting only the distinct ones).

The product of its (nonzero) digits is 161280, while the sum is 45.

The spelling of 81225918720 in words is "eighty-one billion, two hundred twenty-five million, nine hundred eighteen thousand, seven hundred twenty".