81278305 has 4 divisors (see below), whose sum is σ = 97533972. Its totient is φ = 65022640.

The previous prime is 81278293. The next prime is 81278321. The reversal of 81278305 is 50387218.

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 57775201 + 23503104 = 7601^2 + 4848^2 .

It is not a de Polignac number, because 81278305 - 2⁹ = 81277793 is a prime.

It is an alternating number because its digits alternate between even and odd.

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, 8127826 + ... + 8127835.

It is an arithmetic number, because the mean of its divisors is an integer number (24383493).

Almost surely, 2^81278305 is an apocalyptic number.

It is an amenable number.

81278305 is a deficient number, since it is larger than the sum of its proper divisors (16255667).

81278305 is a wasteful number, since it uses less digits than its factorization.

81278305 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16255666.

The product of its (nonzero) digits is 13440, while the sum is 34.

The square root of 81278305 is about 9015.4481308474. The cubic root of 81278305 is about 433.1698420063.

The spelling of 81278305 in words is "eighty-one million, two hundred seventy-eight thousand, three hundred five".