1997999 has 2 divisors, whose sum is σ = 1998000. Its totient is φ = 1997998.

The previous prime is 1997969. The next prime is 1998019. The reversal of 1997999 is 9997991.

It is a strong prime.

It is an emirp because it is prime and its reverse (9997991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1997999 - 2²⁰ = 949423 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 1997999.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1997939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 998999 + 999000.

It is an arithmetic number, because the mean of its divisors is an integer number (999000).

2^1997999 is an apocalyptic number.

1997999 is a deficient number, since it is larger than the sum of its proper divisors (1).

1997999 is an equidigital number, since it uses as much as digits as its factorization.

1997999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 413343, while the sum is 53.

The square root of 1997999 is about 1413.5059249964. The cubic root of 1997999 is about 125.9500726016.

It can be divided in two parts, 1997 and 999, that multiplied together give a triangular number (1995003 = T₁₉₉₇).

The spelling of 1997999 in words is "one million, nine hundred ninety-seven thousand, nine hundred ninety-nine".