1280665 has 4 divisors (see below), whose sum is σ = 1536804. Its totient is φ = 1024528.

The previous prime is 1280659. The next prime is 1280677. The reversal of 1280665 is 5660821.

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 364816 + 915849 = 604^2 + 957^2 .

It is a cyclic number.

It is not a de Polignac number, because 1280665 - 2⁵ = 1280633 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, 128062 + ... + 128071.

It is an arithmetic number, because the mean of its divisors is an integer number (384201).

2^1280665 is an apocalyptic number.

It is an amenable number.

1280665 is a deficient number, since it is larger than the sum of its proper divisors (256139).

1280665 is an equidigital number, since it uses as much as digits as its factorization.

1280665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 256138.

The product of its (nonzero) digits is 2880, while the sum is 28.

The square root of 1280665 is about 1131.6647029929. The cubic root of 1280665 is about 108.5955044055.

The spelling of 1280665 in words is "one million, two hundred eighty thousand, six hundred sixty-five".