997681 has 2 divisors, whose sum is σ = 997682. Its totient is φ = 997680.

The previous prime is 997663. The next prime is 997693. The reversal of 997681 is 186799.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 781456 + 216225 = 884^2 + 465^2 .

It is an emirp because it is prime and its reverse (186799) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 997681 - 2⁵ = 997649 is a prime.

It is a super-2 number, since 2×997681² = 1990734755522, which contains 22 as substring.

It is a Chen prime.

997681 is a lucky number.

It is not a weakly prime, because it can be changed into another prime (997651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 498840 + 498841.

It is an arithmetic number, because the mean of its divisors is an integer number (498841).

2⁹⁹⁷⁶⁸¹ is an apocalyptic number.

It is an amenable number.

997681 is a deficient number, since it is larger than the sum of its proper divisors (1).

997681 is an equidigital number, since it uses as much as digits as its factorization.

997681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 40.

The square root of 997681 is about 998.8398269993. The cubic root of 997681 is about 99.9226401700.

The spelling of 997681 in words is "nine hundred ninety-seven thousand, six hundred eighty-one".