681941549 has 2 divisors, whose sum is σ = 681941550. Its totient is φ = 681941548.

The previous prime is 681941539. The next prime is 681941563. The reversal of 681941549 is 945149186.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 677560900 + 4380649 = 26030^2 + 2093^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681941549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681941539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340970774 + 340970775.

It is an arithmetic number, because the mean of its divisors is an integer number (340970775).

Almost surely, 2^681941549 is an apocalyptic number.

It is an amenable number.

681941549 is a deficient number, since it is larger than the sum of its proper divisors (1).

681941549 is an equidigital number, since it uses as much as digits as its factorization.

681941549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 311040, while the sum is 47.

The square root of 681941549 is about 26114.0105881881. The cubic root of 681941549 is about 880.2020666314.

The spelling of 681941549 in words is "six hundred eighty-one million, nine hundred forty-one thousand, five hundred forty-nine".