678751220221 has 2 divisors, whose sum is σ = 678751220222. Its totient is φ = 678751220220.

The previous prime is 678751220207. The next prime is 678751220249. The reversal of 678751220221 is 122022157876.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 642981063321 + 35770156900 = 801861^2 + 189130^2 .

It is a cyclic number.

It is not a de Polignac number, because 678751220221 - 2⁷ = 678751220093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (678751220281) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 339375610110 + 339375610111.

It is an arithmetic number, because the mean of its divisors is an integer number (339375610111).

Almost surely, 2^678751220221 is an apocalyptic number.

It is an amenable number.

678751220221 is a deficient number, since it is larger than the sum of its proper divisors (1).

678751220221 is an equidigital number, since it uses as much as digits as its factorization.

678751220221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 188160, while the sum is 43.

The spelling of 678751220221 in words is "six hundred seventy-eight billion, seven hundred fifty-one million, two hundred twenty thousand, two hundred twenty-one".