81217258724 has 72 divisors (see below), whose sum is σ = 170763857208. Its totient is φ = 33682521600.

The previous prime is 81217258723. The next prime is 81217258757. The reversal of 81217258724 is 42785271218.

It can be written as a sum of positive squares in 4 ways, for example, as 4478286400 + 76738972324 = 66920^2 + 277018^2 .

It is a super-2 number, since 2×81217258724² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81217258723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 704774 + ... + 811874.

It is an arithmetic number, because the mean of its divisors is an integer number (2371720239).

Almost surely, 2^81217258724 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 81217258724, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (85381928604).

81217258724 is an abundant number, since it is smaller than the sum of its proper divisors (89546598484).

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

81217258724 is a wasteful number, since it uses less digits than its factorization.

81217258724 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 107245 (or 107236 counting only the distinct ones).

The product of its digits is 501760, while the sum is 47.

The spelling of 81217258724 in words is "eighty-one billion, two hundred seventeen million, two hundred fifty-eight thousand, seven hundred twenty-four".