221216557 has 2 divisors, whose sum is σ = 221216558. Its totient is φ = 221216556.

The previous prime is 221216539. The next prime is 221216579. The reversal of 221216557 is 755612122.

221216557 is nontrivially palindromic in base 16.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 220849321 + 367236 = 14861^2 + 606^2 .

It is a cyclic number.

It is not a de Polignac number, because 221216557 - 2¹¹ = 221214509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221216537) 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, 110608278 + 110608279.

It is an arithmetic number, because the mean of its divisors is an integer number (110608279).

Almost surely, 2^221216557 is an apocalyptic number.

It is an amenable number.

221216557 is a deficient number, since it is larger than the sum of its proper divisors (1).

221216557 is an equidigital number, since it uses as much as digits as its factorization.

221216557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8400, while the sum is 31.

The square root of 221216557 is about 14873.3505640121. The cubic root of 221216557 is about 604.7917749834.

Adding to 221216557 its reverse (755612122), we get a palindrome (976828679).

It can be divided in two parts, 2212 and 16557, that added together give a square (18769 = 137²).

The spelling of 221216557 in words is "two hundred twenty-one million, two hundred sixteen thousand, five hundred fifty-seven".