81275609 has 4 divisors (see below), whose sum is σ = 82080420. Its totient is φ = 80470800.

The previous prime is 81275591. The next prime is 81275639. The reversal of 81275609 is 90657218.

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 80281600 + 994009 = 8960^2 + 997^2 .

It is a cyclic number.

It is not a de Polignac number, because 81275609 - 2²⁰ = 80227033 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81275639) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 402254 + ... + 402455.

It is an arithmetic number, because the mean of its divisors is an integer number (20520105).

Almost surely, 2^81275609 is an apocalyptic number.

It is an amenable number.

81275609 is a deficient number, since it is larger than the sum of its proper divisors (804811).

81275609 is a wasteful number, since it uses less digits than its factorization.

81275609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 804810.

The product of its (nonzero) digits is 30240, while the sum is 38.

The square root of 81275609 is about 9015.2986084766. The cubic root of 81275609 is about 433.1650525412.

The spelling of 81275609 in words is "eighty-one million, two hundred seventy-five thousand, six hundred nine".