221455561 has 2 divisors, whose sum is σ = 221455562. Its totient is φ = 221455560.

The previous prime is 221455541. The next prime is 221455567. The reversal of 221455561 is 165554122.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 191545600 + 29909961 = 13840^2 + 5469^2 .

It is a cyclic number.

It is not a de Polignac number, because 221455561 - 2⁷ = 221455433 is a prime.

It is not a weakly prime, because it can be changed into another prime (221455567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110727780 + 110727781.

It is an arithmetic number, because the mean of its divisors is an integer number (110727781).

Almost surely, 2^221455561 is an apocalyptic number.

It is an amenable number.

221455561 is a deficient number, since it is larger than the sum of its proper divisors (1).

221455561 is an equidigital number, since it uses as much as digits as its factorization.

221455561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12000, while the sum is 31.

The square root of 221455561 is about 14881.3830338447. The cubic root of 221455561 is about 605.0095037553.

It can be divided in two parts, 2214 and 55561, that added together give a palindrome (57775).

The spelling of 221455561 in words is "two hundred twenty-one million, four hundred fifty-five thousand, five hundred sixty-one".