1991573 has 2 divisors, whose sum is σ = 1991574. Its totient is φ = 1991572.

The previous prime is 1991551. The next prime is 1991597. The reversal of 1991573 is 3751991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1697809 + 293764 = 1303^2 + 542^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991573 - 2¹² = 1987477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1991503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995786 + 995787.

It is an arithmetic number, because the mean of its divisors is an integer number (995787).

2^1991573 is an apocalyptic number.

It is an amenable number.

1991573 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991573 is an equidigital number, since it uses as much as digits as its factorization.

1991573 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8505, while the sum is 35.

The square root of 1991573 is about 1411.2310229016. The cubic root of 1991573 is about 125.8148999600.

The spelling of 1991573 in words is "one million, nine hundred ninety-one thousand, five hundred seventy-three".