688641905 has 32 divisors (see below), whose sum is σ = 980287488. Its totient is φ = 454449600.

The previous prime is 688641893. The next prime is 688641907. The reversal of 688641905 is 509146886.

It is not a de Polignac number, because 688641905 - 2⁶ = 688641841 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 688641905.

It is not an unprimeable number, because it can be changed into a prime (688641907) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 205574 + ... + 208896.

It is an arithmetic number, because the mean of its divisors is an integer number (30633984).

Almost surely, 2^688641905 is an apocalyptic number.

It is an amenable number.

688641905 is a deficient number, since it is larger than the sum of its proper divisors (291645583).

688641905 is a wasteful number, since it uses less digits than its factorization.

688641905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3557.

The product of its (nonzero) digits is 414720, while the sum is 47.

The square root of 688641905 is about 26241.9874437894. The cubic root of 688641905 is about 883.0754586834.

The spelling of 688641905 in words is "six hundred eighty-eight million, six hundred forty-one thousand, nine hundred five".