688631081 has 2 divisors, whose sum is σ = 688631082. Its totient is φ = 688631080.

The previous prime is 688631057. The next prime is 688631089. The reversal of 688631081 is 180136886.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 683299600 + 5331481 = 26140^2 + 2309^2 .

It is a cyclic number.

It is not a de Polignac number, because 688631081 - 2¹⁸ = 688368937 is a prime.

It is a super-2 number, since 2×688631081² = 948425531438457122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (688631089) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344315540 + 344315541.

It is an arithmetic number, because the mean of its divisors is an integer number (344315541).

Almost surely, 2^688631081 is an apocalyptic number.

It is an amenable number.

688631081 is a deficient number, since it is larger than the sum of its proper divisors (1).

688631081 is an equidigital number, since it uses as much as digits as its factorization.

688631081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 55296, while the sum is 41.

The square root of 688631081 is about 26241.7812085994. The cubic root of 688631081 is about 883.0708319638.

The spelling of 688631081 in words is "six hundred eighty-eight million, six hundred thirty-one thousand, eighty-one".