681989729 has 2 divisors, whose sum is σ = 681989730. Its totient is φ = 681989728.

The previous prime is 681989687. The next prime is 681989741. The reversal of 681989729 is 927989186.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 640090000 + 41899729 = 25300^2 + 6473^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681989729 is a prime.

It is a super-2 number, since 2×681989729² = 930219980922986882, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (681989779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340994864 + 340994865.

It is an arithmetic number, because the mean of its divisors is an integer number (340994865).

Almost surely, 2^681989729 is an apocalyptic number.

It is an amenable number.

681989729 is a deficient number, since it is larger than the sum of its proper divisors (1).

681989729 is an equidigital number, since it uses as much as digits as its factorization.

681989729 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3919104, while the sum is 59.

The square root of 681989729 is about 26114.9330652024. The cubic root of 681989729 is about 880.2227952588. Note that the first 3 decimals are identical.

The spelling of 681989729 in words is "six hundred eighty-one million, nine hundred eighty-nine thousand, seven hundred twenty-nine".