1791991 has 2 divisors, whose sum is σ = 1791992. Its totient is φ = 1791990.

The previous prime is 1791989. The next prime is 1792013. The reversal of 1791991 is 1991971.

1791991 = 544² + 545² + ... + 549².

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 1791991 - 2¹ = 1791989 is a prime.

It is a super-2 number, since 2×1791991² = 6422463488162, which contains 22 as substring.

Together with 1791989, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 1791991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1791901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 895995 + 895996.

It is an arithmetic number, because the mean of its divisors is an integer number (895996).

2^1791991 is an apocalyptic number.

1791991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1791991 is an equidigital number, since it uses as much as digits as its factorization.

1791991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5103, while the sum is 37.

The square root of 1791991 is about 1338.6526808698. The cubic root of 1791991 is about 121.4633555317.

The spelling of 1791991 in words is "one million, seven hundred ninety-one thousand, nine hundred ninety-one".