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19661 is a prime number
BaseRepresentation
bin100110011001101
3222222012
410303031
51112121
6231005
7111215
oct46315
928865
1019661
1113854
12b465
138c45
147245
155c5b
hex4ccd

19661 has 2 divisors, whose sum is σ = 19662. Its totient is φ = 19660.

The previous prime is 19609. The next prime is 19681. The reversal of 19661 is 16691.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17161 + 2500 = 131^2 + 50^2 .

It is an emirp because it is prime and its reverse (16691) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 19661 - 26 = 19597 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9830 + 9831.

It is an arithmetic number, because the mean of its divisors is an integer number (9831).

219661 is an apocalyptic number.

It is an amenable number.

19661 is a deficient number, since it is larger than the sum of its proper divisors (1).

19661 is an equidigital number, since it uses as much as digits as its factorization.

19661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 324, while the sum is 23.

The square root of 19661 is about 140.2176878999. The cubic root of 19661 is about 26.9899368076.

The spelling of 19661 in words is "nineteen thousand, six hundred sixty-one".