688445257 has 2 divisors, whose sum is σ = 688445258. Its totient is φ = 688445256.

The previous prime is 688445231. The next prime is 688445279. The reversal of 688445257 is 752544886.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 546811456 + 141633801 = 23384^2 + 11901^2 .

It is a cyclic number.

It is not a de Polignac number, because 688445257 - 2²³ = 680056649 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 688445257.

It is not a weakly prime, because it can be changed into another prime (688445287) 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, 344222628 + 344222629.

It is an arithmetic number, because the mean of its divisors is an integer number (344222629).

Almost surely, 2^688445257 is an apocalyptic number.

It is an amenable number.

688445257 is a deficient number, since it is larger than the sum of its proper divisors (1).

688445257 is an equidigital number, since it uses as much as digits as its factorization.

688445257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2150400, while the sum is 49.

The square root of 688445257 is about 26238.2403563959. The cubic root of 688445257 is about 882.9913939207.

The spelling of 688445257 in words is "six hundred eighty-eight million, four hundred forty-five thousand, two hundred fifty-seven".