221385821 has 2 divisors, whose sum is σ = 221385822. Its totient is φ = 221385820.

The previous prime is 221385803. The next prime is 221385847. The reversal of 221385821 is 128583122.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 112996900 + 108388921 = 10630^2 + 10411^2 .

It is a cyclic number.

It is not a de Polignac number, because 221385821 - 2⁶ = 221385757 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221385121) 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, 110692910 + 110692911.

It is an arithmetic number, because the mean of its divisors is an integer number (110692911).

Almost surely, 2^221385821 is an apocalyptic number.

It is an amenable number.

221385821 is a deficient number, since it is larger than the sum of its proper divisors (1).

221385821 is an equidigital number, since it uses as much as digits as its factorization.

221385821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7680, while the sum is 32.

The square root of 221385821 is about 14879.0396531497. The cubic root of 221385821 is about 604.9459879382.

The spelling of 221385821 in words is "two hundred twenty-one million, three hundred eighty-five thousand, eight hundred twenty-one".