688216409 has 2 divisors, whose sum is σ = 688216410. Its totient is φ = 688216408.

The previous prime is 688216393. The next prime is 688216427. The reversal of 688216409 is 904612886.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 596727184 + 91489225 = 24428^2 + 9565^2 .

It is a cyclic number.

It is not a de Polignac number, because 688216409 - 2⁴ = 688216393 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 688216409.

It is not a weakly prime, because it can be changed into another prime (688210409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344108204 + 344108205.

It is an arithmetic number, because the mean of its divisors is an integer number (344108205).

Almost surely, 2^688216409 is an apocalyptic number.

It is an amenable number.

688216409 is a deficient number, since it is larger than the sum of its proper divisors (1).

688216409 is an equidigital number, since it uses as much as digits as its factorization.

688216409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 165888, while the sum is 44.

The square root of 688216409 is about 26233.8790307495. The cubic root of 688216409 is about 882.8935438704.

The spelling of 688216409 in words is "six hundred eighty-eight million, two hundred sixteen thousand, four hundred nine".