681241661 has 2 divisors, whose sum is σ = 681241662. Its totient is φ = 681241660.

The previous prime is 681241643. The next prime is 681241699. The reversal of 681241661 is 166142186.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 642876025 + 38365636 = 25355^2 + 6194^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681241661 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681291661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340620830 + 340620831.

It is an arithmetic number, because the mean of its divisors is an integer number (340620831).

Almost surely, 2^681241661 is an apocalyptic number.

It is an amenable number.

681241661 is a deficient number, since it is larger than the sum of its proper divisors (1).

681241661 is an equidigital number, since it uses as much as digits as its factorization.

681241661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 35.

The square root of 681241661 is about 26100.6065255197. The cubic root of 681241661 is about 879.9008415304.

The spelling of 681241661 in words is "six hundred eighty-one million, two hundred forty-one thousand, six hundred sixty-one".