681221 has 2 divisors, whose sum is σ = 681222. Its totient is φ = 681220.

The previous prime is 681179. The next prime is 681229. The reversal of 681221 is 122186.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 624100 + 57121 = 790^2 + 239^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-681221 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a plaindrome in base 6.

It is a junction number, because it is equal to n+sod(n) for n = 681193 and 681202.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (681229) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 340610 + 340611.

It is an arithmetic number, because the mean of its divisors is an integer number (340611).

2⁶⁸¹²²¹ is an apocalyptic number.

It is an amenable number.

681221 is a deficient number, since it is larger than the sum of its proper divisors (1).

681221 is an equidigital number, since it uses as much as digits as its factorization.

681221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 192, while the sum is 20.

The square root of 681221 is about 825.3611330805. The cubic root of 681221 is about 87.9891946099.

It can be divided in two parts, 68 and 1221, that multiplied together give a triangular number (83028 = T₄₀₇).

The spelling of 681221 in words is "six hundred eighty-one thousand, two hundred twenty-one".