217116421 has 2 divisors, whose sum is σ = 217116422. Its totient is φ = 217116420.

The previous prime is 217116391. The next prime is 217116433. The reversal of 217116421 is 124611712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 151019521 + 66096900 = 12289^2 + 8130^2 .

It is a cyclic number.

It is not a de Polignac number, because 217116421 - 2¹⁵ = 217083653 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217116121) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108558210 + 108558211.

It is an arithmetic number, because the mean of its divisors is an integer number (108558211).

Almost surely, 2^217116421 is an apocalyptic number.

It is an amenable number.

217116421 is a deficient number, since it is larger than the sum of its proper divisors (1).

217116421 is an equidigital number, since it uses as much as digits as its factorization.

217116421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 672, while the sum is 25.

The square root of 217116421 is about 14734.8709190138. The cubic root of 217116421 is about 601.0319472720.

The spelling of 217116421 in words is "two hundred seventeen million, one hundred sixteen thousand, four hundred twenty-one".