1991351 has 2 divisors, whose sum is σ = 1991352. Its totient is φ = 1991350.

The previous prime is 1991293. The next prime is 1991357. The reversal of 1991351 is 1531991.

It is a strong prime.

It is an emirp because it is prime and its reverse (1531991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1991351 - 2¹⁰ = 1990327 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991357) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995675 + 995676.

It is an arithmetic number, because the mean of its divisors is an integer number (995676).

2^1991351 is an apocalyptic number.

1991351 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991351 is an equidigital number, since it uses as much as digits as its factorization.

1991351 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1215, while the sum is 29.

The square root of 1991351 is about 1411.1523659761. The cubic root of 1991351 is about 125.8102249375.

The spelling of 1991351 in words is "one million, nine hundred ninety-one thousand, three hundred fifty-one".