221081621 has 2 divisors, whose sum is σ = 221081622. Its totient is φ = 221081620.

The previous prime is 221081611. The next prime is 221081657. The reversal of 221081621 is 126180122.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 135722500 + 85359121 = 11650^2 + 9239^2 .

It is a cyclic number.

It is not a de Polignac number, because 221081621 - 2¹⁴ = 221065237 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (221081611) 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, 110540810 + 110540811.

It is an arithmetic number, because the mean of its divisors is an integer number (110540811).

Almost surely, 2^221081621 is an apocalyptic number.

It is an amenable number.

221081621 is a deficient number, since it is larger than the sum of its proper divisors (1).

221081621 is an equidigital number, since it uses as much as digits as its factorization.

221081621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 221081621 is about 14868.8137052019. The cubic root of 221081621 is about 604.6687812036.

The spelling of 221081621 in words is "two hundred twenty-one million, eighty-one thousand, six hundred twenty-one".