681557771 has 2 divisors, whose sum is σ = 681557772. Its totient is φ = 681557770.

The previous prime is 681557743. The next prime is 681557777. The reversal of 681557771 is 177755186.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 681557771 - 2¹⁰ = 681556747 is a prime.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (681557777) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340778885 + 340778886.

It is an arithmetic number, because the mean of its divisors is an integer number (340778886).

Almost surely, 2^681557771 is an apocalyptic number.

681557771 is a deficient number, since it is larger than the sum of its proper divisors (1).

681557771 is an equidigital number, since it uses as much as digits as its factorization.

681557771 is an evil number, because the sum of its binary digits is even.

The product of its digits is 411600, while the sum is 47.

The square root of 681557771 is about 26106.6614296045. The cubic root of 681557771 is about 880.0369177866.

The spelling of 681557771 in words is "six hundred eighty-one million, five hundred fifty-seven thousand, seven hundred seventy-one".