216509729 has 2 divisors, whose sum is σ = 216509730. Its totient is φ = 216509728.

The previous prime is 216509719. The next prime is 216509749. The reversal of 216509729 is 927905612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 111344704 + 105165025 = 10552^2 + 10255^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-216509729 is a prime.

It is not a weakly prime, because it can be changed into another prime (216509719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108254864 + 108254865.

It is an arithmetic number, because the mean of its divisors is an integer number (108254865).

Almost surely, 2^216509729 is an apocalyptic number.

It is an amenable number.

216509729 is a deficient number, since it is larger than the sum of its proper divisors (1).

216509729 is an equidigital number, since it uses as much as digits as its factorization.

216509729 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 68040, while the sum is 41.

The square root of 216509729 is about 14714.2695707262. The cubic root of 216509729 is about 600.4716005208.

The spelling of 216509729 in words is "two hundred sixteen million, five hundred nine thousand, seven hundred twenty-nine".