217969921 has 8 divisors (see below), whose sum is σ = 234851904. Its totient is φ = 201104400.

The previous prime is 217969901. The next prime is 217969933. The reversal of 217969921 is 129969712.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217969921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217969901) 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, 46746 + ... + 51196.

It is an arithmetic number, because the mean of its divisors is an integer number (29356488).

Almost surely, 2^217969921 is an apocalyptic number.

It is an amenable number.

217969921 is a deficient number, since it is larger than the sum of its proper divisors (16881983).

217969921 is a wasteful number, since it uses less digits than its factorization.

217969921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8231.

The product of its digits is 122472, while the sum is 46.

The square root of 217969921 is about 14763.8044216252. The cubic root of 217969921 is about 601.8184838851.

The spelling of 217969921 in words is "two hundred seventeen million, nine hundred sixty-nine thousand, nine hundred twenty-one".