81281250 has 126 divisors (see below), whose sum is σ = 233844663. Its totient is φ = 20400000.

The previous prime is 81281243. The next prime is 81281257. The reversal of 81281250 is 5218218.

It is an interprime number because it is at equal distance from previous prime (81281243) and next prime (81281257).

It can be written as a sum of positive squares in 11 ways, for example, as 51108201 + 30173049 = 7149^2 + 5493^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=6375.

It is not an unprimeable number, because it can be changed into a prime (81281257) by changing a digit.

It is a polite number, since it can be written in 62 ways as a sum of consecutive naturals, for example, 4781242 + ... + 4781258.

Almost surely, 2^81281250 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81281250

81281250 is an abundant number, since it is smaller than the sum of its proper divisors (152563413).

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

81281250 is an equidigital number, since it uses as much as digits as its factorization.

81281250 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72 (or 27 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 81281250 is about 9015.6114601285. The cubic root of 81281250 is about 433.1750737008.

Adding to 81281250 its reverse (5218218), we get a palindrome (86499468).

The spelling of 81281250 in words is "eighty-one million, two hundred eighty-one thousand, two hundred fifty".