21223651 has 2 divisors, whose sum is σ = 21223652. Its totient is φ = 21223650.

The previous prime is 21223637. The next prime is 21223661. The reversal of 21223651 is 15632212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21223651 - 2⁵ = 21223619 is a prime.

It is not a weakly prime, because it can be changed into another prime (21223661) 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, 10611825 + 10611826.

It is an arithmetic number, because the mean of its divisors is an integer number (10611826).

Almost surely, 2^21223651 is an apocalyptic number.

21223651 is a deficient number, since it is larger than the sum of its proper divisors (1).

21223651 is an equidigital number, since it uses as much as digits as its factorization.

21223651 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 720, while the sum is 22.

The square root of 21223651 is about 4606.9133918493. The cubic root of 21223651 is about 276.8683835619.

Adding to 21223651 its reverse (15632212), we get a palindrome (36855863).

The spelling of 21223651 in words is "twenty-one million, two hundred twenty-three thousand, six hundred fifty-one".