521021 has 2 divisors, whose sum is σ = 521022. Its totient is φ = 521020.

The previous prime is 521009. The next prime is 521023. The reversal of 521021 is 120125.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 436921 + 84100 = 661^2 + 290^2 .

It is a cyclic number.

It is not a de Polignac number, because 521021 - 2⁶ = 520957 is a prime.

It is a Sophie Germain prime.

Together with 521023, 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 = 520993 and 521011.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 521021.

It is not a weakly prime, because it can be changed into another prime (521023) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 260510 + 260511.

It is an arithmetic number, because the mean of its divisors is an integer number (260511).

2⁵²¹⁰²¹ is an apocalyptic number.

It is an amenable number.

521021 is a deficient number, since it is larger than the sum of its proper divisors (1).

521021 is an equidigital number, since it uses as much as digits as its factorization.

521021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20, while the sum is 11.

The square root of 521021 is about 721.8178440576. The cubic root of 521021 is about 80.4671110327.

Adding to 521021 its reverse (120125), we get a palindrome (641146).

The spelling of 521021 in words is "five hundred twenty-one thousand, twenty-one".