688639639 has 2 divisors, whose sum is σ = 688639640. Its totient is φ = 688639638.

The previous prime is 688639607. The next prime is 688639657. The reversal of 688639639 is 936936886.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 688639639 - 2⁵ = 688639607 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (688639669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344319819 + 344319820.

It is an arithmetic number, because the mean of its divisors is an integer number (344319820).

Almost surely, 2^688639639 is an apocalyptic number.

688639639 is a deficient number, since it is larger than the sum of its proper divisors (1).

688639639 is an equidigital number, since it uses as much as digits as its factorization.

688639639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10077696, while the sum is 58.

The square root of 688639639 is about 26241.9442686703. The cubic root of 688639639 is about 883.0744900855.

The spelling of 688639639 in words is "six hundred eighty-eight million, six hundred thirty-nine thousand, six hundred thirty-nine".