4021 has 2 divisors, whose sum is σ = 4022.
Its totient is φ = 4020.
The previous prime is 4019. The next prime is 4027. The reversal of 4021 is 1204.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 2500 + 1521 = 50^2 + 39^2
It is a cyclic number.
It is not a de Polignac number, because 4021 - 21 = 4019 is a prime.
Together with 4019, it forms a pair of twin primes.
It is a nialpdrome in base 8 and base 16.
It is a junction number, because it is equal to n+sod(n) for n = 3995 and 4013.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (4027) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2010 + 2011.
It is an arithmetic number, because the mean of its divisors is an integer number (2011).
24021 is an apocalyptic number.
It is an amenable number.
4021 is a deficient number, since it is larger than the sum of its proper divisors (1).
4021 is an equidigital number, since it uses as much as digits as its factorization.
4021 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 8, while the sum is 7.
The square root of 4021 is about 63.4113554500.
The cubic root of 4021 is about 15.9017415652.
Adding to 4021 its reverse (1204), we get a palindrome (5225).
The spelling of 4021 in words is "four thousand, twenty-one", and thus it is an iban number.