688971538 has 4 divisors (see below), whose sum is σ = 1033457310. Its totient is φ = 344485768.

The previous prime is 688971533. The next prime is 688971557. The reversal of 688971538 is 835179886.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 835179886 = 2 ⋅417589943.

It can be written as a sum of positive squares in only one way, i.e., 671690889 + 17280649 = 25917^2 + 4157^2 .

It is not an unprimeable number, because it can be changed into a prime (688971533) 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, 172242883 + ... + 172242886.

Almost surely, 2^688971538 is an apocalyptic number.

688971538 is a deficient number, since it is larger than the sum of its proper divisors (344485772).

688971538 is a wasteful number, since it uses less digits than its factorization.

688971538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 344485771.

The product of its digits is 2903040, while the sum is 55.

The square root of 688971538 is about 26248.2673332927. The cubic root of 688971538 is about 883.2163371173.

The spelling of 688971538 in words is "six hundred eighty-eight million, nine hundred seventy-one thousand, five hundred thirty-eight".