1280639 has 8 divisors (see below), whose sum is σ = 1326672. Its totient is φ = 1235520.

The previous prime is 1280633. The next prime is 1280651. The reversal of 1280639 is 9360821.

1280639 is nontrivially palindromic in base 9.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1280639 - 2⁴ = 1280623 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1280633) 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 7 ways as a sum of consecutive naturals, for example, 3704 + ... + 4034.

It is an arithmetic number, because the mean of its divisors is an integer number (165834).

2^1280639 is an apocalyptic number.

1280639 is a deficient number, since it is larger than the sum of its proper divisors (46033).

1280639 is an equidigital number, since it uses as much as digits as its factorization.

1280639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 457.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 1280639 is about 1131.6532154331. The cubic root of 1280639 is about 108.5947695003.

The spelling of 1280639 in words is "one million, two hundred eighty thousand, six hundred thirty-nine".