21224981 has 2 divisors, whose sum is σ = 21224982. Its totient is φ = 21224980.

The previous prime is 21224971. The next prime is 21224989. The reversal of 21224981 is 18942212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16072081 + 5152900 = 4009^2 + 2270^2 .

It is a cyclic number.

It is not a de Polignac number, because 21224981 - 2¹⁰ = 21223957 is a prime.

It is a super-2 number, since 2×21224981² = 900999636900722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen 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 (21224989) 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, 10612490 + 10612491.

It is an arithmetic number, because the mean of its divisors is an integer number (10612491).

Almost surely, 2^21224981 is an apocalyptic number.

It is an amenable number.

21224981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21224981 is an equidigital number, since it uses as much as digits as its factorization.

21224981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2304, while the sum is 29.

The square root of 21224981 is about 4607.0577378626. The cubic root of 21224981 is about 276.8741668468.

The spelling of 21224981 in words is "twenty-one million, two hundred twenty-four thousand, nine hundred eighty-one".