81361265 has 4 divisors (see below), whose sum is σ = 97633524. Its totient is φ = 65089008.

The previous prime is 81361253. The next prime is 81361279. The reversal of 81361265 is 56216318.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 38837824 + 42523441 = 6232^2 + 6521^2 .

It is a cyclic number.

It is not a de Polignac number, because 81361265 - 2¹⁰ = 81360241 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8136122 + ... + 8136131.

It is an arithmetic number, because the mean of its divisors is an integer number (24408381).

Almost surely, 2^81361265 is an apocalyptic number.

It is an amenable number.

81361265 is a deficient number, since it is larger than the sum of its proper divisors (16272259).

81361265 is a wasteful number, since it uses less digits than its factorization.

81361265 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16272258.

The product of its digits is 8640, while the sum is 32.

The square root of 81361265 is about 9020.0479488748. The cubic root of 81361265 is about 433.3171693510.

The spelling of 81361265 in words is "eighty-one million, three hundred sixty-one thousand, two hundred sixty-five".