681239621 has 2 divisors, whose sum is σ = 681239622. Its totient is φ = 681239620.

The previous prime is 681239617. The next prime is 681239639. The reversal of 681239621 is 126932186.

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., 562211521 + 119028100 = 23711^2 + 10910^2 .

It is a cyclic number.

It is not a de Polignac number, because 681239621 - 2² = 681239617 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681239651) 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, 340619810 + 340619811.

It is an arithmetic number, because the mean of its divisors is an integer number (340619811).

Almost surely, 2^681239621 is an apocalyptic number.

It is an amenable number.

681239621 is a deficient number, since it is larger than the sum of its proper divisors (1).

681239621 is an equidigital number, since it uses as much as digits as its factorization.

681239621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 31104, while the sum is 38.

The square root of 681239621 is about 26100.5674459388. The cubic root of 681239621 is about 879.8999632324.

The spelling of 681239621 in words is "six hundred eighty-one million, two hundred thirty-nine thousand, six hundred twenty-one".