521009 has 2 divisors, whose sum is σ = 521010. Its totient is φ = 521008.

The previous prime is 520981. The next prime is 521021. The reversal of 521009 is 900125.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 418609 + 102400 = 647^2 + 320^2 .

It is a cyclic number.

It is not a de Polignac number, because 521009 - 2¹⁶ = 455473 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (521039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 260504 + 260505.

It is an arithmetic number, because the mean of its divisors is an integer number (260505).

2⁵²¹⁰⁰⁹ is an apocalyptic number.

It is an amenable number.

521009 is a deficient number, since it is larger than the sum of its proper divisors (1).

521009 is an equidigital number, since it uses as much as digits as its factorization.

521009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 90, while the sum is 17.

The square root of 521009 is about 721.8095316633. The cubic root of 521009 is about 80.4664932631.

The spelling of 521009 in words is "five hundred twenty-one thousand, nine".