1688405 has 4 divisors (see below), whose sum is σ = 2026092. Its totient is φ = 1350720.

The previous prime is 1688387. The next prime is 1688411. The reversal of 1688405 is 5048861.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1136356 + 552049 = 1066^2 + 743^2 .

It is not a de Polignac number, because 1688405 - 2⁶ = 1688341 is a prime.

It is a super-2 number, since 2×1688405² = 5701422888050, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

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, 168836 + ... + 168845.

It is an arithmetic number, because the mean of its divisors is an integer number (506523).

2^1688405 is an apocalyptic number.

It is an amenable number.

1688405 is a deficient number, since it is larger than the sum of its proper divisors (337687).

1688405 is an equidigital number, since it uses as much as digits as its factorization.

1688405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 337686.

The product of its (nonzero) digits is 7680, while the sum is 32.

The square root of 1688405 is about 1299.3863936489. The cubic root of 1688405 is about 119.0763580267.

It can be divided in two parts, 168 and 8405, that multiplied together give a triangular number (1412040 = T₁₆₈₀).

The spelling of 1688405 in words is "one million, six hundred eighty-eight thousand, four hundred five".