217723993 has 8 divisors (see below), whose sum is σ = 222129000. Its totient is φ = 213362688.

The previous prime is 217723991. The next prime is 217723997. The reversal of 217723993 is 399327712.

It can be written as a sum of positive squares in 4 ways, for example, as 5817744 + 211906249 = 2412^2 + 14557^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 217723993 - 2¹ = 217723991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217723991) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 768 + ... + 20881.

It is an arithmetic number, because the mean of its divisors is an integer number (27766125).

Almost surely, 2^217723993 is an apocalyptic number.

It is an amenable number.

217723993 is a deficient number, since it is larger than the sum of its proper divisors (4405007).

217723993 is a wasteful number, since it uses less digits than its factorization.

217723993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21851.

The product of its digits is 142884, while the sum is 43.

The square root of 217723993 is about 14755.4733234824. The cubic root of 217723993 is about 601.5920616446.

The spelling of 217723993 in words is "two hundred seventeen million, seven hundred twenty-three thousand, nine hundred ninety-three".