1688981 has 6 divisors (see below), whose sum is σ = 1964790. Its totient is φ = 1447656.

The previous prime is 1688977. The next prime is 1688987. The reversal of 1688981 is 1898861.

It can be written as a sum of positive squares in only one way, i.e., 1500625 + 188356 = 1225^2 + 434^2 .

It is not a de Polignac number, because 1688981 - 2² = 1688977 is a prime.

It is a super-2 number, since 2×1688981² = 5705313636722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1688987) 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 5 ways as a sum of consecutive naturals, for example, 17186 + ... + 17283.

It is an arithmetic number, because the mean of its divisors is an integer number (327465).

2^1688981 is an apocalyptic number.

It is an amenable number.

1688981 is a deficient number, since it is larger than the sum of its proper divisors (275809).

1688981 is an equidigital number, since it uses as much as digits as its factorization.

1688981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34483 (or 34476 counting only the distinct ones).

The product of its digits is 27648, while the sum is 41.

The square root of 1688981 is about 1299.6080178269. The cubic root of 1688981 is about 119.0898974686.

The spelling of 1688981 in words is "one million, six hundred eighty-eight thousand, nine hundred eighty-one".