19997 has 2 divisors, whose sum is σ = 19998. Its totient is φ = 19996.

The previous prime is 19993. The next prime is 20011. The reversal of 19997 is 79991.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19321 + 676 = 139^2 + 26^2 .

It is a cyclic number.

It is not a de Polignac number, because 19997 - 2² = 19993 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 (19991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9998 + 9999.

It is an arithmetic number, because the mean of its divisors is an integer number (9999).

2¹⁹⁹⁹⁷ is an apocalyptic number.

It is an amenable number.

19997 is a deficient number, since it is larger than the sum of its proper divisors (1).

19997 is an equidigital number, since it uses as much as digits as its factorization.

19997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5103, while the sum is 35.

The square root of 19997 is about 141.4107492378. The cubic root of 19997 is about 27.1428188893.

The spelling of 19997 in words is "nineteen thousand, nine hundred ninety-seven".