1021 has 2 divisors, whose sum is σ = 1022.
Its totient is φ = 1020.
The previous prime is 1019. The next prime is 1031. The reversal of 1021 is 1201.
It is a weak prime.
It can be written as a sum of positive squares in only one way, i.e., 900 + 121 = 30^2 + 11^2
It is an emirp because it is prime and its reverse (1201) is a distict prime.
It is a cyclic number.
It is not a de Polignac number, because 1021 - 21 = 1019 is a prime.
Together with 1019, it forms a pair of twin primes.
1021 is a lucky number.
It is a nialpdrome in base 4, base 6 and base 12.
It is a self number, because there is not a number n which added to its sum of digits gives 1021.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (1031) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510 + 511.
It is an arithmetic number, because the mean of its divisors is an integer number (511).
It is an amenable number.
1021 is a deficient number, since it is larger than the sum of its proper divisors (1).
1021 is an equidigital number, since it uses as much as digits as its factorization.
1021 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 2, while the sum is 4.
The square root of 1021 is about 31.9530906173.
The cubic root of 1021 is about 10.0695156378.
Adding to 1021 its reverse (1201), we get a palindrome (2222).
Multiplying 1021 by its reverse (1201), we get a palindrome (1226221).
It can be divided in two parts, 10 and 21, that multiplied together give a triangular number (210 = T20).
The spelling of 1021 in words is "one thousand, twenty-one", and thus it is an iban number.