21242651 has 2 divisors, whose sum is σ = 21242652. Its totient is φ = 21242650.

The previous prime is 21242629. The next prime is 21242659. The reversal of 21242651 is 15624212.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21242651 - 2¹⁸ = 20980507 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21242659) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621325 + 10621326.

It is an arithmetic number, because the mean of its divisors is an integer number (10621326).

Almost surely, 2^21242651 is an apocalyptic number.

21242651 is a deficient number, since it is larger than the sum of its proper divisors (1).

21242651 is an equidigital number, since it uses as much as digits as its factorization.

21242651 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 21242651 is about 4608.9750487500. The cubic root of 21242651 is about 276.9509790004.

Adding to 21242651 its reverse (15624212), we get a palindrome (36866863).

The spelling of 21242651 in words is "twenty-one million, two hundred forty-two thousand, six hundred fifty-one".