216722309 has 4 divisors (see below), whose sum is σ = 217137216. Its totient is φ = 216307404.

The previous prime is 216722299. The next prime is 216722321. The reversal of 216722309 is 903227612.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 216722309 - 2⁴ = 216722293 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216722509) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 206669 + ... + 207714.

It is an arithmetic number, because the mean of its divisors is an integer number (54284304).

Almost surely, 2^216722309 is an apocalyptic number.

It is an amenable number.

216722309 is a deficient number, since it is larger than the sum of its proper divisors (414907).

216722309 is an equidigital number, since it uses as much as digits as its factorization.

216722309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 414906.

The product of its (nonzero) digits is 9072, while the sum is 32.

The square root of 216722309 is about 14721.4913986321. The cubic root of 216722309 is about 600.6680605121.

The spelling of 216722309 in words is "two hundred sixteen million, seven hundred twenty-two thousand, three hundred nine".