1991707 has 2 divisors, whose sum is σ = 1991708. Its totient is φ = 1991706.

The previous prime is 1991681. The next prime is 1991723. The reversal of 1991707 is 7071991.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (7071991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1991707 - 2¹⁹ = 1467419 is a prime.

1991707 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (1991797) 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, 995853 + 995854.

It is an arithmetic number, because the mean of its divisors is an integer number (995854).

2^1991707 is an apocalyptic number.

1991707 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991707 is an equidigital number, since it uses as much as digits as its factorization.

1991707 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3969, while the sum is 34.

The square root of 1991707 is about 1411.2784983836. The cubic root of 1991707 is about 125.8177216523.

The spelling of 1991707 in words is "one million, nine hundred ninety-one thousand, seven hundred seven".