686481221 has 2 divisors, whose sum is σ = 686481222. Its totient is φ = 686481220.

The previous prime is 686481203. The next prime is 686481223. The reversal of 686481221 is 122184686.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 670240321 + 16240900 = 25889^2 + 4030^2 .

It is a cyclic number.

It is not a de Polignac number, because 686481221 - 2¹⁸ = 686219077 is a prime.

Together with 686481223, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (686481223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343240610 + 343240611.

It is an arithmetic number, because the mean of its divisors is an integer number (343240611).

Almost surely, 2^686481221 is an apocalyptic number.

It is an amenable number.

686481221 is a deficient number, since it is larger than the sum of its proper divisors (1).

686481221 is an equidigital number, since it uses as much as digits as its factorization.

686481221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36864, while the sum is 38.

The square root of 686481221 is about 26200.7866484959. The cubic root of 686481221 is about 882.1509113726.

The spelling of 686481221 in words is "six hundred eighty-six million, four hundred eighty-one thousand, two hundred twenty-one".