217250021 has 16 divisors (see below), whose sum is σ = 240126768. Its totient is φ = 195686400.

The previous prime is 217250017. The next prime is 217250039. The reversal of 217250021 is 120052712.

It can be written as a sum of positive squares in 8 ways, for example, as 5692996 + 211557025 = 2386^2 + 14545^2 .

It is a cyclic number.

It is not a de Polignac number, because 217250021 - 2² = 217250017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 217249975 and 217250002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217250041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34001 + ... + 39881.

It is an arithmetic number, because the mean of its divisors is an integer number (15007923).

Almost surely, 2^217250021 is an apocalyptic number.

It is an amenable number.

217250021 is a deficient number, since it is larger than the sum of its proper divisors (22876747).

217250021 is a wasteful number, since it uses less digits than its factorization.

217250021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5992.

The product of its (nonzero) digits is 280, while the sum is 20.

The square root of 217250021 is about 14739.4036853599. The cubic root of 217250021 is about 601.1552012745.

The spelling of 217250021 in words is "two hundred seventeen million, two hundred fifty thousand, twenty-one".