509681 has 2 divisors, whose sum is σ = 509682. Its totient is φ = 509680.

The previous prime is 509659. The next prime is 509687. The reversal of 509681 is 186905.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 429025 + 80656 = 655^2 + 284^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-509681 is a prime.

It is a super-2 number, since 2×509681² = 519549443522, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (509687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 254840 + 254841.

It is an arithmetic number, because the mean of its divisors is an integer number (254841).

2⁵⁰⁹⁶⁸¹ is an apocalyptic number.

It is an amenable number.

509681 is a deficient number, since it is larger than the sum of its proper divisors (1).

509681 is an equidigital number, since it uses as much as digits as its factorization.

509681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2160, while the sum is 29.

The square root of 509681 is about 713.9194632450. The cubic root of 509681 is about 79.8790359384.

The spelling of 509681 in words is "five hundred nine thousand, six hundred eighty-one".