688711561 has 2 divisors, whose sum is σ = 688711562. Its totient is φ = 688711560.

The previous prime is 688711549. The next prime is 688711567. The reversal of 688711561 is 165117886.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 668739600 + 19971961 = 25860^2 + 4469^2 .

It is a cyclic number.

It is not a de Polignac number, because 688711561 - 2⁷ = 688711433 is a prime.

It is a super-2 number, since 2×688711561² = 948647228510113442, which contains 22 as substring.

It is equal to p_35698354 and since 688711561 and 35698354 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (688711567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344355780 + 344355781.

It is an arithmetic number, because the mean of its divisors is an integer number (344355781).

Almost surely, 2^688711561 is an apocalyptic number.

It is an amenable number.

688711561 is a deficient number, since it is larger than the sum of its proper divisors (1).

688711561 is an equidigital number, since it uses as much as digits as its factorization.

688711561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 80640, while the sum is 43.

The square root of 688711561 is about 26243.3145962929. The cubic root of 688711561 is about 883.1052319854.

The spelling of 688711561 in words is "six hundred eighty-eight million, seven hundred eleven thousand, five hundred sixty-one".