217812945 has 32 divisors (see below), whose sum is σ = 402029568. Its totient is φ = 98635968.

The previous prime is 217812943. The next prime is 217812949. The reversal of 217812945 is 549218712.

It is not a de Polignac number, because 217812945 - 2¹ = 217812943 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (217812943) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1542 + ... + 20928.

It is an arithmetic number, because the mean of its divisors is an integer number (12563424).

Almost surely, 2^217812945 is an apocalyptic number.

It is an amenable number.

217812945 is a deficient number, since it is larger than the sum of its proper divisors (184216623).

217812945 is a wasteful number, since it uses less digits than its factorization.

217812945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19509.

The product of its digits is 40320, while the sum is 39.

The square root of 217812945 is about 14758.4872192241. The cubic root of 217812945 is about 601.6739780966.

The spelling of 217812945 in words is "two hundred seventeen million, eight hundred twelve thousand, nine hundred forty-five".