687133781 has 2 divisors, whose sum is σ = 687133782. Its totient is φ = 687133780.

The previous prime is 687133757. The next prime is 687133787. The reversal of 687133781 is 187331786.

687133781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 501356881 + 185776900 = 22391^2 + 13630^2 .

It is a cyclic number.

It is not a de Polignac number, because 687133781 - 2¹⁴ = 687117397 is a prime.

It is a super-2 number, since 2×687133781² = 944305665982711922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (687133787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343566890 + 343566891.

It is an arithmetic number, because the mean of its divisors is an integer number (343566891).

Almost surely, 2^687133781 is an apocalyptic number.

It is an amenable number.

687133781 is a deficient number, since it is larger than the sum of its proper divisors (1).

687133781 is an equidigital number, since it uses as much as digits as its factorization.

687133781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 169344, while the sum is 44.

The square root of 687133781 is about 26213.2367516871. The cubic root of 687133781 is about 882.4303431928.

The spelling of 687133781 in words is "six hundred eighty-seven million, one hundred thirty-three thousand, seven hundred eighty-one".