21401 has 2 divisors, whose sum is σ = 21402.
Its totient is φ = 21400.
The previous prime is 21397. The next prime is 21407. The reversal of 21401 is 10412.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 15625 + 5776 = 125^2 + 76^2
It is a cyclic number.
It is not a de Polignac number, because 21401 - 22 = 21397 is a prime.
It is a Chen prime.
It is a nialpdrome in base 13.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21401.
It is not a weakly prime, because it can be changed into another prime (21407) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10700 + 10701.
It is an arithmetic number, because the mean of its divisors is an integer number (10701).
221401 is an apocalyptic number.
It is an amenable number.
21401 is a deficient number, since it is larger than the sum of its proper divisors (1).
21401 is an equidigital number, since it uses as much as digits as its factorization.
21401 is an evil number, because the sum of its binary digits is even.
The product of its (nonzero) digits is 8, while the sum is 8.
The square root of 21401 is about 146.2908062730.
The cubic root of 21401 is about 27.7637434290.
Adding to 21401 its reverse (10412), we get a palindrome (31813).
The spelling of 21401 in words is "twenty-one thousand, four hundred one", and thus it is an iban number.