81438890625 has 63 divisors (see below), whose sum is σ = 147234033349. Its totient is φ = 43377000000.

The previous prime is 81438890501. The next prime is 81438890629. The reversal of 81438890625 is 52609883418.

The square root of 81438890625 is 285375.

It is a perfect power (a square), and thus also a powerful number.

81438890625 is a `hidden beast` number, since 8 + 1 + 4 + 3 + 8 + 8 + 9 + 0 + 625 = 666.

It can be written as a sum of positive squares in 10 ways, for example, as 12998052081 + 68440838544 = 114009^2 + 261612^2 .

It is not a de Polignac number, because 81438890625 - 2¹⁹ = 81438366337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81438890629) 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 62 ways as a sum of consecutive naturals, for example, 107015245 + ... + 107016005.

Almost surely, 2^81438890625 is an apocalyptic number.

81438890625 is the 285375-th square number.

81438890625 is the 142688-th centered octagonal number.

It is an amenable number.

81438890625 is a deficient number, since it is larger than the sum of its proper divisors (65795142724).

81438890625 is an frugal number, since it uses more digits than its factorization.

81438890625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1558 (or 769 counting only the distinct ones).

The product of its (nonzero) digits is 3317760, while the sum is 54.

The spelling of 81438890625 in words is "eighty-one billion, four hundred thirty-eight million, eight hundred ninety thousand, six hundred twenty-five".