217021913 has 2 divisors, whose sum is σ = 217021914. Its totient is φ = 217021912.

The previous prime is 217021891. The next prime is 217021921. The reversal of 217021913 is 319120712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 169728784 + 47293129 = 13028^2 + 6877^2 .

It is a cyclic number.

It is not a de Polignac number, because 217021913 - 2⁸ = 217021657 is a prime.

It is not a weakly prime, because it can be changed into another prime (217021963) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108510956 + 108510957.

It is an arithmetic number, because the mean of its divisors is an integer number (108510957).

Almost surely, 2^217021913 is an apocalyptic number.

It is an amenable number.

217021913 is a deficient number, since it is larger than the sum of its proper divisors (1).

217021913 is an equidigital number, since it uses as much as digits as its factorization.

217021913 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 756, while the sum is 26.

The square root of 217021913 is about 14731.6636195645. The cubic root of 217021913 is about 600.9447274434.

The spelling of 217021913 in words is "two hundred seventeen million, twenty-one thousand, nine hundred thirteen".