221164561 has 2 divisors, whose sum is σ = 221164562. Its totient is φ = 221164560.

The previous prime is 221164553. The next prime is 221164583. The reversal of 221164561 is 165461122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 220225600 + 938961 = 14840^2 + 969^2 .

It is a cyclic number.

It is not a de Polignac number, because 221164561 - 2³ = 221164553 is a prime.

It is not a weakly prime, because it can be changed into another prime (221164061) 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, 110582280 + 110582281.

It is an arithmetic number, because the mean of its divisors is an integer number (110582281).

Almost surely, 2^221164561 is an apocalyptic number.

It is an amenable number.

221164561 is a deficient number, since it is larger than the sum of its proper divisors (1).

221164561 is an equidigital number, since it uses as much as digits as its factorization.

221164561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2880, while the sum is 28.

The square root of 221164561 is about 14871.6025027567. The cubic root of 221164561 is about 604.7443867021.

The spelling of 221164561 in words is "two hundred twenty-one million, one hundred sixty-four thousand, five hundred sixty-one".