1687989 has 4 divisors (see below), whose sum is σ = 2250656. Its totient is φ = 1125324.

The previous prime is 1687969. The next prime is 1687991. The reversal of 1687989 is 9897861.

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.

It is a de Polignac number, because none of the positive numbers 2^k-1687989 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 (1687909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 281329 + ... + 281334.

It is an arithmetic number, because the mean of its divisors is an integer number (562664).

2^1687989 is an apocalyptic number.

It is an amenable number.

1687989 is a deficient number, since it is larger than the sum of its proper divisors (562667).

1687989 is an equidigital number, since it uses as much as digits as its factorization.

1687989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 562666.

The product of its digits is 217728, while the sum is 48.

The square root of 1687989 is about 1299.2263082312. The cubic root of 1687989 is about 119.0665776257.

The spelling of 1687989 in words is "one million, six hundred eighty-seven thousand, nine hundred eighty-nine".