221858921 has 2 divisors, whose sum is σ = 221858922. Its totient is φ = 221858920.

The previous prime is 221858867. The next prime is 221858929. The reversal of 221858921 is 129858122.

221858921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 211848025 + 10010896 = 14555^2 + 3164^2 .

It is a cyclic number.

It is not a de Polignac number, because 221858921 - 2¹⁰ = 221857897 is a prime.

It is not a weakly prime, because it can be changed into another prime (221858929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 110929460 + 110929461.

It is an arithmetic number, because the mean of its divisors is an integer number (110929461).

Almost surely, 2^221858921 is an apocalyptic number.

It is an amenable number.

221858921 is a deficient number, since it is larger than the sum of its proper divisors (1).

221858921 is an equidigital number, since it uses as much as digits as its factorization.

221858921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23040, while the sum is 38.

The square root of 221858921 is about 14894.9293721051. The cubic root of 221858921 is about 605.3766031694.

The spelling of 221858921 in words is "two hundred twenty-one million, eight hundred fifty-eight thousand, nine hundred twenty-one".