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19861 is a prime number
BaseRepresentation
bin100110110010101
31000020121
410312111
51113421
6231541
7111622
oct46625
930217
1019861
1113a16
12b5b1
13906a
147349
155d41
hex4d95

19861 has 2 divisors, whose sum is σ = 19862. Its totient is φ = 19860.

The previous prime is 19853. The next prime is 19867. The reversal of 19861 is 16891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11025 + 8836 = 105^2 + 94^2 .

It is a cyclic number.

It is not a de Polignac number, because 19861 - 23 = 19853 is a prime.

19861 is a strobogrammatic number because it is the same when read upside-down.

19861 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19867) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9930 + 9931.

It is an arithmetic number, because the mean of its divisors is an integer number (9931).

219861 is an apocalyptic number.

It is an amenable number.

19861 is a deficient number, since it is larger than the sum of its proper divisors (1).

19861 is an equidigital number, since it uses as much as digits as its factorization.

19861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432, while the sum is 25.

The square root of 19861 is about 140.9290601686. The cubic root of 19861 is about 27.0811459114.

The spelling of 19861 in words is "nineteen thousand, eight hundred sixty-one".