217215261 has 6 divisors (see below), whose sum is σ = 313755390. Its totient is φ = 144810168.

The previous prime is 217215259. The next prime is 217215283. The reversal of 217215261 is 162512712.

It can be written as a sum of positive squares in only one way, i.e., 143856036 + 73359225 = 11994^2 + 8565^2 .

It is not a de Polignac number, because 217215261 - 2¹ = 217215259 is a prime.

It is a super-2 number, since 2×217215261² = 94364939222596242, which contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217215221) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 12067506 + ... + 12067523.

It is an arithmetic number, because the mean of its divisors is an integer number (52292565).

Almost surely, 2^217215261 is an apocalyptic number.

It is an amenable number.

217215261 is a deficient number, since it is larger than the sum of its proper divisors (96540129).

217215261 is a wasteful number, since it uses less digits than its factorization.

217215261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24135035 (or 24135032 counting only the distinct ones).

The product of its digits is 1680, while the sum is 27.

The square root of 217215261 is about 14738.2244860092. The cubic root of 217215261 is about 601.1231379567.

Adding to 217215261 its reverse (162512712), we get a palindrome (379727973).

The spelling of 217215261 in words is "two hundred seventeen million, two hundred fifteen thousand, two hundred sixty-one".