1287681 has 4 divisors (see below), whose sum is σ = 1716912. Its totient is φ = 858452.

The previous prime is 1287661. The next prime is 1287683. The reversal of 1287681 is 1867821.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1867821 = 3 ⋅622607.

It is a cyclic number.

It is not a de Polignac number, because 1287681 - 2⁷ = 1287553 is a prime.

It is a super-2 number, since 2×1287681² = 3316244715522, which contains 22 as substring.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (1287683) 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, 214611 + ... + 214616.

It is an arithmetic number, because the mean of its divisors is an integer number (429228).

2^1287681 is an apocalyptic number.

It is an amenable number.

1287681 is a deficient number, since it is larger than the sum of its proper divisors (429231).

1287681 is an equidigital number, since it uses as much as digits as its factorization.

1287681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 429230.

The product of its digits is 5376, while the sum is 33.

The square root of 1287681 is about 1134.7603271176. The cubic root of 1287681 is about 108.7934533709.

The spelling of 1287681 in words is "one million, two hundred eighty-seven thousand, six hundred eighty-one".