681621737 has 2 divisors, whose sum is σ = 681621738. Its totient is φ = 681621736.

The previous prime is 681621727. The next prime is 681621739. The reversal of 681621737 is 737126186.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 477160336 + 204461401 = 21844^2 + 14299^2 .

It is a cyclic number.

It is not a de Polignac number, because 681621737 - 2⁶ = 681621673 is a prime.

Together with 681621739, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 681621694 and 681621703.

It is not a weakly prime, because it can be changed into another prime (681621739) 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, 340810868 + 340810869.

It is an arithmetic number, because the mean of its divisors is an integer number (340810869).

Almost surely, 2^681621737 is an apocalyptic number.

It is an amenable number.

681621737 is a deficient number, since it is larger than the sum of its proper divisors (1).

681621737 is an equidigital number, since it uses as much as digits as its factorization.

681621737 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 84672, while the sum is 41.

The square root of 681621737 is about 26107.8864904841. The cubic root of 681621737 is about 880.0644481897.

The spelling of 681621737 in words is "six hundred eighty-one million, six hundred twenty-one thousand, seven hundred thirty-seven".