81909265 has 4 divisors (see below), whose sum is σ = 98291124. Its totient is φ = 65527408.

The previous prime is 81909259. The next prime is 81909271. The reversal of 81909265 is 56290918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56290918 = 2 ⋅28145459.

It is an interprime number because it is at equal distance from previous prime (81909259) and next prime (81909271).

It can be written as a sum of positive squares in 2 ways, for example, as 43877376 + 38031889 = 6624^2 + 6167^2 .

It is a cyclic number.

It is not a de Polignac number, because 81909265 - 2¹³ = 81901073 is a prime.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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, 8190922 + ... + 8190931.

It is an arithmetic number, because the mean of its divisors is an integer number (24572781).

Almost surely, 2^81909265 is an apocalyptic number.

It is an amenable number.

81909265 is a deficient number, since it is larger than the sum of its proper divisors (16381859).

81909265 is a wasteful number, since it uses less digits than its factorization.

81909265 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16381858.

The product of its (nonzero) digits is 38880, while the sum is 40.

The square root of 81909265 is about 9050.3737491885. The cubic root of 81909265 is about 434.2878469455.

The spelling of 81909265 in words is "eighty-one million, nine hundred nine thousand, two hundred sixty-five".