21104221 has 2 divisors, whose sum is σ = 21104222. Its totient is φ = 21104220.

The previous prime is 21104203. The next prime is 21104233. The reversal of 21104221 is 12240112.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14784025 + 6320196 = 3845^2 + 2514^2 .

It is a cyclic number.

It is not a de Polignac number, because 21104221 - 2¹³ = 21096029 is a prime.

It is a super-3 number, since 3×21104221³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21104921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10552110 + 10552111.

It is an arithmetic number, because the mean of its divisors is an integer number (10552111).

Almost surely, 2^21104221 is an apocalyptic number.

It is an amenable number.

21104221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21104221 is an equidigital number, since it uses as much as digits as its factorization.

21104221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 21104221 is about 4593.9330643796. The cubic root of 21104221 is about 276.3480739389.

Adding to 21104221 its reverse (12240112), we get a palindrome (33344333).

It can be divided in two parts, 2110 and 4221, that multiplied together give a triangular number (8906310 = T₄₂₂₀).

The spelling of 21104221 in words is "twenty-one million, one hundred four thousand, two hundred twenty-one".