688675781 has 4 divisors (see below), whose sum is σ = 698954592. Its totient is φ = 678396972.

The previous prime is 688675759. The next prime is 688675807. The reversal of 688675781 is 187576886.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 688675781 - 2⁶ = 688675717 is a prime.

It is a super-2 number, since 2×688675781² = 948548662671919922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688675711) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5139305 + ... + 5139438.

It is an arithmetic number, because the mean of its divisors is an integer number (174738648).

Almost surely, 2^688675781 is an apocalyptic number.

It is an amenable number.

688675781 is a deficient number, since it is larger than the sum of its proper divisors (10278811).

688675781 is a wasteful number, since it uses less digits than its factorization.

688675781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10278810.

The product of its digits is 4515840, while the sum is 56.

The square root of 688675781 is about 26242.6328900132. The cubic root of 688675781 is about 883.0899386685.

The spelling of 688675781 in words is "six hundred eighty-eight million, six hundred seventy-five thousand, seven hundred eighty-one".