21456221 has 2 divisors, whose sum is σ = 21456222. Its totient is φ = 21456220.

The previous prime is 21456203. The next prime is 21456251. The reversal of 21456221 is 12265412.

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., 21436900 + 19321 = 4630^2 + 139^2 .

It is a cyclic number.

It is not a de Polignac number, because 21456221 - 2⁶ = 21456157 is a prime.

It is a super-3 number, since 3×21456221³ (a number of 23 digits) contains 333 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21456251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10728110 + 10728111.

It is an arithmetic number, because the mean of its divisors is an integer number (10728111).

Almost surely, 2^21456221 is an apocalyptic number.

It is an amenable number.

21456221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21456221 is an equidigital number, since it uses as much as digits as its factorization.

21456221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 960, while the sum is 23.

The square root of 21456221 is about 4632.0860311527. The cubic root of 21456221 is about 277.8760251519.

The spelling of 21456221 in words is "twenty-one million, four hundred fifty-six thousand, two hundred twenty-one".