16670421216721 has 2 divisors, whose sum is σ = 16670421216722. Its totient is φ = 16670421216720.

The previous prime is 16670421216643. The next prime is 16670421216797. The reversal of 16670421216721 is 12761212407661.

16670421216721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15932583166096 + 737838050625 = 3991564^2 + 858975^2 .

It is a cyclic number.

It is not a de Polignac number, because 16670421216721 - 2⁹ = 16670421216209 is a prime.

It is not a weakly prime, because it can be changed into another prime (16670421216221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8335210608360 + 8335210608361.

It is an arithmetic number, because the mean of its divisors is an integer number (8335210608361).

Almost surely, 2^{16670421216721} is an apocalyptic number.

It is an amenable number.

16670421216721 is a deficient number, since it is larger than the sum of its proper divisors (1).

16670421216721 is an equidigital number, since it uses as much as digits as its factorization.

16670421216721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 338688, while the sum is 46.

The spelling of 16670421216721 in words is "sixteen trillion, six hundred seventy billion, four hundred twenty-one million, two hundred sixteen thousand, seven hundred twenty-one".