81549725424 has 320 divisors, whose sum is σ = 236916264960. Its totient is φ = 24053760000.

The previous prime is 81549725423. The next prime is 81549725429. The reversal of 81549725424 is 42452794518.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81549725423) 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, 150738594 + ... + 150739134.

It is an arithmetic number, because the mean of its divisors is an integer number (740363328).

Almost surely, 2^81549725424 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 81549725424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118458132480).

81549725424 is an abundant number, since it is smaller than the sum of its proper divisors (155366539536).

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

81549725424 is a wasteful number, since it uses less digits than its factorization.

81549725424 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 760 (or 754 counting only the distinct ones).

The product of its digits is 3225600, while the sum is 51.

The spelling of 81549725424 in words is "eighty-one billion, five hundred forty-nine million, seven hundred twenty-five thousand, four hundred twenty-four".