216505170509 has 4 divisors (see below), whose sum is σ = 225918438816. Its totient is φ = 207091902204.

The previous prime is 216505170491. The next prime is 216505170571. The reversal of 216505170509 is 905071505612.

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 not a de Polignac number, because 216505170509 - 2¹⁶ = 216505104973 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216505110509) 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, 4706634119 + ... + 4706634164.

It is an arithmetic number, because the mean of its divisors is an integer number (56479609704).

Almost surely, 2^216505170509 is an apocalyptic number.

It is an amenable number.

216505170509 is a deficient number, since it is larger than the sum of its proper divisors (9413268307).

216505170509 is an equidigital number, since it uses as much as digits as its factorization.

216505170509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9413268306.

The product of its (nonzero) digits is 94500, while the sum is 41.

The spelling of 216505170509 in words is "two hundred sixteen billion, five hundred five million, one hundred seventy thousand, five hundred nine".