1999691 has 2 divisors, whose sum is σ = 1999692. Its totient is φ = 1999690.

The previous prime is 1999681. The next prime is 1999703. The reversal of 1999691 is 1969991.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1999691 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (1999631) 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 as a sum of consecutive naturals, namely, 999845 + 999846.

It is an arithmetic number, because the mean of its divisors is an integer number (999846).

2^1999691 is an apocalyptic number.

1999691 is a deficient number, since it is larger than the sum of its proper divisors (1).

1999691 is an equidigital number, since it uses as much as digits as its factorization.

1999691 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 39366, while the sum is 44.

The square root of 1999691 is about 1414.1043101554. The cubic root of 1999691 is about 125.9856160619.

The spelling of 1999691 in words is "one million, nine hundred ninety-nine thousand, six hundred ninety-one".