217919939 has 2 divisors, whose sum is σ = 217919940. Its totient is φ = 217919938.

The previous prime is 217919929. The next prime is 217919951. The reversal of 217919939 is 939919712.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217919939 is a prime.

It is not a weakly prime, because it can be changed into another prime (217919929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108959969 + 108959970.

It is an arithmetic number, because the mean of its divisors is an integer number (108959970).

Almost surely, 2^217919939 is an apocalyptic number.

217919939 is a deficient number, since it is larger than the sum of its proper divisors (1).

217919939 is an equidigital number, since it uses as much as digits as its factorization.

217919939 is an evil number, because the sum of its binary digits is even.

The product of its digits is 275562, while the sum is 50.

The square root of 217919939 is about 14762.1116036968. Note that the first 3 decimals coincide. The cubic root of 217919939 is about 601.7724799980.

The spelling of 217919939 in words is "two hundred seventeen million, nine hundred nineteen thousand, nine hundred thirty-nine".