217812961 has 2 divisors, whose sum is σ = 217812962. Its totient is φ = 217812960.

The previous prime is 217812949. The next prime is 217812971. The reversal of 217812961 is 169218712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 133980625 + 83832336 = 11575^2 + 9156^2 .

It is a cyclic number.

It is not a de Polignac number, because 217812961 - 2⁵ = 217812929 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 217812961.

It is not a weakly prime, because it can be changed into another prime (217812901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108906480 + 108906481.

It is an arithmetic number, because the mean of its divisors is an integer number (108906481).

Almost surely, 2^217812961 is an apocalyptic number.

It is an amenable number.

217812961 is a deficient number, since it is larger than the sum of its proper divisors (1).

217812961 is an equidigital number, since it uses as much as digits as its factorization.

217812961 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 37.

The square root of 217812961 is about 14758.4877612850. The cubic root of 217812961 is about 601.6739928291.

It can be divided in two parts, 21781 and 2961, that added together give a palindrome (24742).

The spelling of 217812961 in words is "two hundred seventeen million, eight hundred twelve thousand, nine hundred sixty-one".