221555557 has 2 divisors, whose sum is σ = 221555558. Its totient is φ = 221555556.

The previous prime is 221555549. The next prime is 221555567. The reversal of 221555557 is 755555122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 215766721 + 5788836 = 14689^2 + 2406^2 .

It is a cyclic number.

It is not a de Polignac number, because 221555557 - 2³ = 221555549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221555507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110777778 + 110777779.

It is an arithmetic number, because the mean of its divisors is an integer number (110777779).

Almost surely, 2^221555557 is an apocalyptic number.

It is an amenable number.

221555557 is a deficient number, since it is larger than the sum of its proper divisors (1).

221555557 is an equidigital number, since it uses as much as digits as its factorization.

221555557 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 87500, while the sum is 37.

The square root of 221555557 is about 14884.7424230317. The cubic root of 221555557 is about 605.1005520097.

The spelling of 221555557 in words is "two hundred twenty-one million, five hundred fifty-five thousand, five hundred fifty-seven".