19961 has 2 divisors, whose sum is σ = 19962. Its totient is φ = 19960.

The previous prime is 19949. The next prime is 19963. The reversal of 19961 is 16991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19600 + 361 = 140^2 + 19^2 .It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 19661 and 16691.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19961 is a prime.

Together with 19963, it forms a pair of twin primes.

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 19961.

It is not a weakly prime, because it can be changed into another prime (19963) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9980 + 9981.

It is an arithmetic number, because the mean of its divisors is an integer number (9981).

2¹⁹⁹⁶¹ is an apocalyptic number.

It is an amenable number.

19961 is a deficient number, since it is larger than the sum of its proper divisors (1).

19961 is an equidigital number, since it uses as much as digits as its factorization.

19961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 486, while the sum is 26.

The square root of 19961 is about 141.2834031300. The cubic root of 19961 is about 27.1265209706.

The spelling of 19961 in words is "nineteen thousand, nine hundred sixty-one".