1688391 has 8 divisors (see below), whose sum is σ = 2501360. Its totient is φ = 1125576.

The previous prime is 1688387. The next prime is 1688411. The reversal of 1688391 is 1938861.

It is not a de Polignac number, because 1688391 - 2² = 1688387 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 (1688311) 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 7 ways as a sum of consecutive naturals, for example, 31240 + ... + 31293.

It is an arithmetic number, because the mean of its divisors is an integer number (312670).

2^1688391 is an apocalyptic number.

1688391 is a deficient number, since it is larger than the sum of its proper divisors (812969).

1688391 is an equidigital number, since it uses as much as digits as its factorization.

1688391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62542 (or 62536 counting only the distinct ones).

The product of its digits is 10368, while the sum is 36.

The square root of 1688391 is about 1299.3810064796. The cubic root of 1688391 is about 119.0760289047.

The spelling of 1688391 in words is "one million, six hundred eighty-eight thousand, three hundred ninety-one".