688773781 has 4 divisors (see below), whose sum is σ = 688826272. Its totient is φ = 688721292.

The previous prime is 688773749. The next prime is 688773791. The reversal of 688773781 is 187377886.

688773781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 688773781 - 2⁵ = 688773749 is a prime.

It is a super-2 number, since 2×688773781² = 948818642786071922, which contains 22 as substring.

It is the 26245-th Hogben number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (688773791) by changing a digit.

It is a nontrivial repunit in base 26244.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12880 + ... + 39286.

It is an arithmetic number, because the mean of its divisors is an integer number (172206568).

It is a 13122-hyperperfect number.

Almost surely, 2^688773781 is an apocalyptic number.

It is an amenable number.

688773781 is a deficient number, since it is larger than the sum of its proper divisors (52491).

688773781 is a wasteful number, since it uses less digits than its factorization.

688773781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52490.

The product of its digits is 3161088, while the sum is 55.

The square root of 688773781 is about 26244.5000142887. The cubic root of 688773781 is about 883.1318251951.

The spelling of 688773781 in words is "six hundred eighty-eight million, seven hundred seventy-three thousand, seven hundred eighty-one".