1891997 has 2 divisors, whose sum is σ = 1891998. Its totient is φ = 1891996.

The previous prime is 1891991. The next prime is 1892017. The reversal of 1891997 is 7991981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1585081 + 306916 = 1259^2 + 554^2 .

1891997 is a truncatable prime.

It is an emirp because it is prime and its reverse (7991981) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1891997 - 2⁶ = 1891933 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 (1891991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 945998 + 945999.

It is an arithmetic number, because the mean of its divisors is an integer number (945999).

2^1891997 is an apocalyptic number.

It is an amenable number.

1891997 is a deficient number, since it is larger than the sum of its proper divisors (1).

1891997 is an equidigital number, since it uses as much as digits as its factorization.

1891997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40824, while the sum is 44.

The square root of 1891997 is about 1375.4988186109. The cubic root of 1891997 is about 123.6820897336.

The spelling of 1891997 in words is "one million, eight hundred ninety-one thousand, nine hundred ninety-seven".