1681691 has 18 divisors (see below), whose sum is σ = 2037252. Its totient is φ = 1376320.

The previous prime is 1681679. The next prime is 1681703. The reversal of 1681691 is 1961861.

It is an interprime number because it is at equal distance from previous prime (1681679) and next prime (1681703).

It is a de Polignac number, because none of the positive numbers 2^k-1681691 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1681621) 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 17 ways as a sum of consecutive naturals, for example, 73106 + ... + 73128.

2^1681691 is an apocalyptic number.

1681691 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1681691 is a deficient number, since it is larger than the sum of its proper divisors (355561).

1681691 is a wasteful number, since it uses less digits than its factorization.

1681691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 91 (or 51 counting only the distinct ones).

The product of its digits is 2592, while the sum is 32.

The square root of 1681691 is about 1296.8002930290. The cubic root of 1681691 is about 118.9183112838.

The spelling of 1681691 in words is "one million, six hundred eighty-one thousand, six hundred ninety-one".