81091105225 has 45 divisors (see below), whose sum is σ = 109256291097. Its totient is φ = 59704968960.

The previous prime is 81091105181. The next prime is 81091105229. The reversal of 81091105225 is 52250119018.

The square root of 81091105225 is 284765.

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

It can be written as a sum of positive squares in 22 ways, for example, as 12784146489 + 68306958736 = 113067^2 + 261356^2 .

It is not a de Polignac number, because 81091105225 - 2²¹ = 81089008073 is a prime.

It is a super-2 number, since 2×81091105225² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81091105229) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 240626257 + ... + 240626593.

Almost surely, 2^81091105225 is an apocalyptic number.

81091105225 is the 284765-th square number.

81091105225 is the 142383-rd centered octagonal number.

It is an amenable number.

81091105225 is a deficient number, since it is larger than the sum of its proper divisors (28165185872).

81091105225 is an frugal number, since it uses more digits than its factorization.

81091105225 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 736 (or 355 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 34.

The spelling of 81091105225 in words is "eighty-one billion, ninety-one million, one hundred five thousand, two hundred twenty-five".