688905009 has 27 divisors (see below), whose sum is σ = 1079121537. Its totient is φ = 423311616.

The previous prime is 688904981. The next prime is 688905011. The reversal of 688905009 is 900509886.

The square root of 688905009 is 26247.

It is a perfect power (a square), and thus also a powerful number.

688905009 is a `hidden beast` number, since 68 + 89 + 0 + 500 + 9 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 198725409 + 490179600 = 14097^2 + 22140^2 .

It is not a de Polignac number, because 688905009 - 2²⁹ = 152034097 is a prime.

It is a super-2 number, since 2×688905009² = 949180222850580162, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (688905029) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 1023297 + ... + 1023969.

Almost surely, 2^688905009 is an apocalyptic number.

688905009 is the 26247-th square number.

688905009 is the 13124-th centered octagonal number.

It is an amenable number.

688905009 is a deficient number, since it is larger than the sum of its proper divisors (390216528).

688905009 is an equidigital number, since it uses as much as digits as its factorization.

688905009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1378 (or 689 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 45.

The cubic root of 688905009 is about 883.1879075970.

The spelling of 688905009 in words is "six hundred eighty-eight million, nine hundred five thousand, nine".