21224431 has 2 divisors, whose sum is σ = 21224432. Its totient is φ = 21224430.

The previous prime is 21224389. The next prime is 21224447. The reversal of 21224431 is 13442212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21224431 - 2¹⁹ = 20700143 is a prime.

It is a super-2 number, since 2×21224431² = 900952942547522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21224399 and 21224408.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21224131) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10612215 + 10612216.

It is an arithmetic number, because the mean of its divisors is an integer number (10612216).

Almost surely, 2^21224431 is an apocalyptic number.

21224431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21224431 is an equidigital number, since it uses as much as digits as its factorization.

21224431 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 384, while the sum is 19.

The square root of 21224431 is about 4606.9980464506. The cubic root of 21224431 is about 276.8717752921.

Adding to 21224431 its reverse (13442212), we get a palindrome (34666643).

The spelling of 21224431 in words is "twenty-one million, two hundred twenty-four thousand, four hundred thirty-one".