21004550221 has 2 divisors, whose sum is σ = 21004550222. Its totient is φ = 21004550220.

The previous prime is 21004550201. The next prime is 21004550251. The reversal of 21004550221 is 12205540012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17818512196 + 3186038025 = 133486^2 + 56445^2 .

It is a cyclic number.

It is not a de Polignac number, because 21004550221 - 2⁷ = 21004550093 is a prime.

It is a super-2 number, since 2×21004550221² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21004550192 and 21004550201.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21004550201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502275110 + 10502275111.

It is an arithmetic number, because the mean of its divisors is an integer number (10502275111).

Almost surely, 2^21004550221 is an apocalyptic number.

It is an amenable number.

21004550221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004550221 is an equidigital number, since it uses as much as digits as its factorization.

21004550221 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 800, while the sum is 22.

The spelling of 21004550221 in words is "twenty-one billion, four million, five hundred fifty thousand, two hundred twenty-one".