681593921 has 2 divisors, whose sum is σ = 681593922. Its totient is φ = 681593920.

The previous prime is 681593911. The next prime is 681593981. The reversal of 681593921 is 129395186.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 530795521 + 150798400 = 23039^2 + 12280^2 .

It is a cyclic number.

It is not a de Polignac number, because 681593921 - 2¹⁴ = 681577537 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (681593911) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340796960 + 340796961.

It is an arithmetic number, because the mean of its divisors is an integer number (340796961).

Almost surely, 2^681593921 is an apocalyptic number.

It is an amenable number.

681593921 is a deficient number, since it is larger than the sum of its proper divisors (1).

681593921 is an equidigital number, since it uses as much as digits as its factorization.

681593921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 116640, while the sum is 44.

The square root of 681593921 is about 26107.3537724527. The cubic root of 681593921 is about 880.0524766399.

The spelling of 681593921 in words is "six hundred eighty-one million, five hundred ninety-three thousand, nine hundred twenty-one".