1281639 has 4 divisors (see below), whose sum is σ = 1708856. Its totient is φ = 854424.

The previous prime is 1281587. The next prime is 1281649. The reversal of 1281639 is 9361821.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 1281639 - 2⁸ = 1281383 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1281649) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 213604 + ... + 213609.

It is an arithmetic number, because the mean of its divisors is an integer number (427214).

2^1281639 is an apocalyptic number.

1281639 is a deficient number, since it is larger than the sum of its proper divisors (427217).

1281639 is an equidigital number, since it uses as much as digits as its factorization.

1281639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 427216.

The product of its digits is 2592, while the sum is 30.

The square root of 1281639 is about 1132.0949606813. The cubic root of 1281639 is about 108.6230279234.

The spelling of 1281639 in words is "one million, two hundred eighty-one thousand, six hundred thirty-nine".