16421 has 2 divisors, whose sum is σ = 16422. Its totient is φ = 16420.
The previous prime is 16417. The next prime is 16427. The reversal of 16421 is 12461.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 9025 + 7396 = 95^2 + 86^2 .
It is a cyclic number.
It is not a de Polignac number, because 16421 - 22 = 16417 is a prime.
It is a Sophie Germain prime.
It is a Chen prime.
It is an Ulam number.
It is a Curzon number.
It is a plaindrome in base 11.
It is a nialpdrome in base 13.
It is a junction number, because it is equal to n+sod(n) for n = 16396 and 16405.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (16427) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8210 + 8211.
It is an arithmetic number, because the mean of its divisors is an integer number (8211).
216421 is an apocalyptic number.
It is an amenable number.
16421 is a deficient number, since it is larger than the sum of its proper divisors (1).
16421 is an equidigital number, since it uses as much as digits as its factorization.
16421 is an evil number, because the sum of its binary digits is even.
The product of its digits is 48, while the sum is 14.
The square root of 16421 is about 128.1444497432. The cubic root of 16421 is about 25.4175215455.
Adding to 16421 its reverse (12461), we get a palindrome (28882).
The spelling of 16421 in words is "sixteen thousand, four hundred twenty-one".
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