216709321 has 2 divisors, whose sum is σ = 216709322. Its totient is φ = 216709320.

The previous prime is 216709303. The next prime is 216709327. The reversal of 216709321 is 123907612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 128142400 + 88566921 = 11320^2 + 9411^2 .

It is a cyclic number.

It is not a de Polignac number, because 216709321 - 2¹⁵ = 216676553 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (216709327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108354660 + 108354661.

It is an arithmetic number, because the mean of its divisors is an integer number (108354661).

Almost surely, 2^216709321 is an apocalyptic number.

It is an amenable number.

216709321 is a deficient number, since it is larger than the sum of its proper divisors (1).

216709321 is an equidigital number, since it uses as much as digits as its factorization.

216709321 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4536, while the sum is 31.

The square root of 216709321 is about 14721.0502682383. The cubic root of 216709321 is about 600.6560610820.

The spelling of 216709321 in words is "two hundred sixteen million, seven hundred nine thousand, three hundred twenty-one".