684789509 has 2 divisors, whose sum is σ = 684789510. Its totient is φ = 684789508.

The previous prime is 684789493. The next prime is 684789517. The reversal of 684789509 is 905987486.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 396129409 + 288660100 = 19903^2 + 16990^2 .

It is a cyclic number.

It is not a de Polignac number, because 684789509 - 2⁴ = 684789493 is a prime.

It is a super-2 number, since 2×684789509² = 937873343272922162, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (684789709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342394754 + 342394755.

It is an arithmetic number, because the mean of its divisors is an integer number (342394755).

Almost surely, 2^684789509 is an apocalyptic number.

It is an amenable number.

684789509 is a deficient number, since it is larger than the sum of its proper divisors (1).

684789509 is an equidigital number, since it uses as much as digits as its factorization.

684789509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4354560, while the sum is 56.

The square root of 684789509 is about 26168.4831237884. The cubic root of 684789509 is about 881.4256801539.

The spelling of 684789509 in words is "six hundred eighty-four million, seven hundred eighty-nine thousand, five hundred nine".