688499991 has 12 divisors (see below), whose sum is σ = 1028793480. Its totient is φ = 443172240.

The previous prime is 688499957. The next prime is 688500061. The reversal of 688499991 is 199994886.

It is not a de Polignac number, because 688499991 - 2²⁵ = 654945559 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688499951) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1318705 + ... + 1319226.

It is an arithmetic number, because the mean of its divisors is an integer number (85732790).

Almost surely, 2^688499991 is an apocalyptic number.

688499991 is a deficient number, since it is larger than the sum of its proper divisors (340293489).

688499991 is a wasteful number, since it uses less digits than its factorization.

688499991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2637966 (or 2637963 counting only the distinct ones).

The product of its digits is 10077696, while the sum is 63.

The square root of 688499991 is about 26239.2833553053. The cubic root of 688499991 is about 883.0147936849.

The spelling of 688499991 in words is "six hundred eighty-eight million, four hundred ninety-nine thousand, nine hundred ninety-one".