688040731 has 4 divisors (see below), whose sum is σ = 786332272. Its totient is φ = 589749192.

The previous prime is 688040729. The next prime is 688040741. The reversal of 688040731 is 137040886.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 137040886 = 2 ⋅68520443.

It is a cyclic number.

It is not a de Polignac number, because 688040731 - 2¹ = 688040729 is a prime.

It is a super-2 number, since 2×688040731² = 946800095030028722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (688040741) 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 in 3 ways as a sum of consecutive naturals, for example, 49145760 + ... + 49145773.

It is an arithmetic number, because the mean of its divisors is an integer number (196583068).

Almost surely, 2^688040731 is an apocalyptic number.

688040731 is a deficient number, since it is larger than the sum of its proper divisors (98291541).

688040731 is an equidigital number, since it uses as much as digits as its factorization.

688040731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98291540.

The product of its (nonzero) digits is 32256, while the sum is 37.

The square root of 688040731 is about 26230.5305131253. The cubic root of 688040731 is about 882.8184133497.

The spelling of 688040731 in words is "six hundred eighty-eight million, forty thousand, seven hundred thirty-one".