688717639 has 2 divisors, whose sum is σ = 688717640. Its totient is φ = 688717638.

The previous prime is 688717613. The next prime is 688717661. The reversal of 688717639 is 936717886.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 688717639 - 2¹⁹ = 688193351 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 688717639.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (688717609) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344358819 + 344358820.

It is an arithmetic number, because the mean of its divisors is an integer number (344358820).

Almost surely, 2^688717639 is an apocalyptic number.

688717639 is a deficient number, since it is larger than the sum of its proper divisors (1).

688717639 is an equidigital number, since it uses as much as digits as its factorization.

688717639 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3048192, while the sum is 55.

The square root of 688717639 is about 26243.4303969584. The cubic root of 688717639 is about 883.1078298305.

The spelling of 688717639 in words is "six hundred eighty-eight million, seven hundred seventeen thousand, six hundred thirty-nine".