217122021 has 12 divisors (see below), whose sum is σ = 313973920. Its totient is φ = 144585000.

The previous prime is 217121959. The next prime is 217122041. The reversal of 217122021 is 120221712.

It is a happy number.

It is not a de Polignac number, because 217122021 - 2⁷ = 217121893 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 217121985 and 217122003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217122041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4855 + ... + 21396.

Almost surely, 2^217122021 is an apocalyptic number.

It is an amenable number.

217122021 is a deficient number, since it is larger than the sum of its proper divisors (96851899).

217122021 is a wasteful number, since it uses less digits than its factorization.

217122021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27176 (or 27173 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 217122021 is about 14735.0609432062. The cubic root of 217122021 is about 601.0371146225.

Adding to 217122021 its reverse (120221712), we get a palindrome (337343733).

The spelling of 217122021 in words is "two hundred seventeen million, one hundred twenty-two thousand, twenty-one".