1688681 has 2 divisors, whose sum is σ = 1688682. Its totient is φ = 1688680.

The previous prime is 1688677. The next prime is 1688741. The reversal of 1688681 is 1868861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1254400 + 434281 = 1120^2 + 659^2 .

It is a cyclic number.

It is not a de Polignac number, because 1688681 - 2² = 1688677 is a prime.

It is a super-2 number, since 2×1688681² = 5703287039522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1688651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 844340 + 844341.

It is an arithmetic number, because the mean of its divisors is an integer number (844341).

2^1688681 is an apocalyptic number.

It is an amenable number.

1688681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1688681 is an equidigital number, since it uses as much as digits as its factorization.

1688681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18432, while the sum is 38.

The square root of 1688681 is about 1299.4925932840. The cubic root of 1688681 is about 119.0828460601.

The spelling of 1688681 in words is "one million, six hundred eighty-eight thousand, six hundred eighty-one".