1993991 has 2 divisors, whose sum is σ = 1993992. Its totient is φ = 1993990.

The previous prime is 1993973. The next prime is 1993997.

1993991 is nontrivially palindromic in base 10.

It is a strong prime.

It is a palprime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1993991 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1993997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 996995 + 996996.

It is an arithmetic number, because the mean of its divisors is an integer number (996996).

2^1993991 is an apocalyptic number.

1993991 is a deficient number, since it is larger than the sum of its proper divisors (1).

1993991 is an equidigital number, since it uses as much as digits as its factorization.

1993991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 19683, while the sum is 41.

The square root of 1993991 is about 1412.0874618805. The cubic root of 1993991 is about 125.8657973146.

The spelling of 1993991 in words is "one million, nine hundred ninety-three thousand, nine hundred ninety-one".