1687691 has 4 divisors (see below), whose sum is σ = 1690584. Its totient is φ = 1684800.

The previous prime is 1687669. The next prime is 1687729. The reversal of 1687691 is 1967861.

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

It is a cyclic number.

It is not a de Polignac number, because 1687691 - 2⁶ = 1687627 is a prime.

It is a super-2 number, since 2×1687691² = 5696601822962, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1687661) 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, 230 + ... + 1851.

It is an arithmetic number, because the mean of its divisors is an integer number (422646).

2^1687691 is an apocalyptic number.

1687691 is a deficient number, since it is larger than the sum of its proper divisors (2893).

1687691 is an equidigital number, since it uses as much as digits as its factorization.

1687691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2892.

The product of its digits is 18144, while the sum is 38.

The square root of 1687691 is about 1299.1116195308. Note that the first 3 decimals coincide. The cubic root of 1687691 is about 119.0595704852.

The spelling of 1687691 in words is "one million, six hundred eighty-seven thousand, six hundred ninety-one".