1020821 has 2 divisors, whose sum is σ = 1020822. Its totient is φ = 1020820.

The previous prime is 1020797. The next prime is 1020823. The reversal of 1020821 is 1280201.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 828100 + 192721 = 910^2 + 439^2 .

It is a cyclic number.

It is not a de Polignac number, because 1020821 - 2⁶ = 1020757 is a prime.

It is a Sophie Germain prime.

Together with 1020823, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 1020796 and 1020805.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1020823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510410 + 510411.

It is an arithmetic number, because the mean of its divisors is an integer number (510411).

2^1020821 is an apocalyptic number.

It is an amenable number.

1020821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1020821 is an equidigital number, since it uses as much as digits as its factorization.

1020821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 1020821 is about 1010.3568676463. The cubic root of 1020821 is about 100.6892714661.

The spelling of 1020821 in words is "one million, twenty thousand, eight hundred twenty-one".