217997951 has 2 divisors, whose sum is σ = 217997952. Its totient is φ = 217997950.

The previous prime is 217997911. The next prime is 217997971. The reversal of 217997951 is 159799712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 217997951 - 2¹⁴ = 217981567 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 217997951.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (217997911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108998975 + 108998976.

It is an arithmetic number, because the mean of its divisors is an integer number (108998976).

Almost surely, 2^217997951 is an apocalyptic number.

217997951 is a deficient number, since it is larger than the sum of its proper divisors (1).

217997951 is an equidigital number, since it uses as much as digits as its factorization.

217997951 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 357210, while the sum is 50.

The square root of 217997951 is about 14764.7536721748. The cubic root of 217997951 is about 601.8442798741.

The spelling of 217997951 in words is "two hundred seventeen million, nine hundred ninety-seven thousand, nine hundred fifty-one".