217912813 has 2 divisors, whose sum is σ = 217912814. Its totient is φ = 217912812.

The previous prime is 217912771. The next prime is 217912819. The reversal of 217912813 is 318219712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 200590569 + 17322244 = 14163^2 + 4162^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217912813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217912819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108956406 + 108956407.

It is an arithmetic number, because the mean of its divisors is an integer number (108956407).

Almost surely, 2^217912813 is an apocalyptic number.

It is an amenable number.

217912813 is a deficient number, since it is larger than the sum of its proper divisors (1).

217912813 is an equidigital number, since it uses as much as digits as its factorization.

217912813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 34.

The square root of 217912813 is about 14761.8702405894. The cubic root of 217912813 is about 601.7659205899.

The spelling of 217912813 in words is "two hundred seventeen million, nine hundred twelve thousand, eight hundred thirteen".