688278121 has 2 divisors, whose sum is σ = 688278122. Its totient is φ = 688278120.

The previous prime is 688278077. The next prime is 688278161. The reversal of 688278121 is 121872886.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 673921600 + 14356521 = 25960^2 + 3789^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-688278121 is a prime.

It is not a weakly prime, because it can be changed into another prime (688278161) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344139060 + 344139061.

It is an arithmetic number, because the mean of its divisors is an integer number (344139061).

Almost surely, 2^688278121 is an apocalyptic number.

It is an amenable number.

688278121 is a deficient number, since it is larger than the sum of its proper divisors (1).

688278121 is an equidigital number, since it uses as much as digits as its factorization.

688278121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 86016, while the sum is 43.

The square root of 688278121 is about 26235.0551933858. The cubic root of 688278121 is about 882.9199326134.

The spelling of 688278121 in words is "six hundred eighty-eight million, two hundred seventy-eight thousand, one hundred twenty-one".