217920945 has 32 divisors (see below), whose sum is σ = 389660544. Its totient is φ = 103078400.

The previous prime is 217920919. The next prime is 217920959. The reversal of 217920945 is 549029712.

It is not a de Polignac number, because 217920945 - 2⁶ = 217920881 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 9342 + ... + 22871.

It is an arithmetic number, because the mean of its divisors is an integer number (12176892).

Almost surely, 2^217920945 is an apocalyptic number.

It is an amenable number.

217920945 is a deficient number, since it is larger than the sum of its proper divisors (171739599).

217920945 is a wasteful number, since it uses less digits than its factorization.

217920945 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32273.

The product of its (nonzero) digits is 45360, while the sum is 39.

The square root of 217920945 is about 14762.1456773736. The cubic root of 217920945 is about 601.7734059989.

The spelling of 217920945 in words is "two hundred seventeen million, nine hundred twenty thousand, nine hundred forty-five".