216951209 has 4 divisors (see below), whose sum is σ = 217034580. Its totient is φ = 216867840.

The previous prime is 216951199. The next prime is 216951223. The reversal of 216951209 is 902159612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 125328025 + 91623184 = 11195^2 + 9572^2 .

It is a cyclic number.

It is not a de Polignac number, because 216951209 - 2¹⁶ = 216885673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (216951289) 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, 37652 + ... + 43029.

It is an arithmetic number, because the mean of its divisors is an integer number (54258645).

Almost surely, 2^216951209 is an apocalyptic number.

It is an amenable number.

216951209 is a deficient number, since it is larger than the sum of its proper divisors (83371).

216951209 is an equidigital number, since it uses as much as digits as its factorization.

216951209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83370.

The product of its (nonzero) digits is 9720, while the sum is 35.

The square root of 216951209 is about 14729.2636951071. The cubic root of 216951209 is about 600.8794593630.

The spelling of 216951209 in words is "two hundred sixteen million, nine hundred fifty-one thousand, two hundred nine".