21236651 has 2 divisors, whose sum is σ = 21236652. Its totient is φ = 21236650.

The previous prime is 21236627. The next prime is 21236653. The reversal of 21236651 is 15663212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21236651 is a prime.

Together with 21236653, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21236651.

It is not a weakly prime, because it can be changed into another prime (21236653) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10618325 + 10618326.

It is an arithmetic number, because the mean of its divisors is an integer number (10618326).

Almost surely, 2^21236651 is an apocalyptic number.

21236651 is a deficient number, since it is larger than the sum of its proper divisors (1).

21236651 is an equidigital number, since it uses as much as digits as its factorization.

21236651 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2160, while the sum is 26.

The square root of 21236651 is about 4608.3240988455. The cubic root of 21236651 is about 276.9249015530.

Adding to 21236651 its reverse (15663212), we get a palindrome (36899863).

It can be divided in two parts, 212 and 36651, that added together give a palindrome (36863).

The spelling of 21236651 in words is "twenty-one million, two hundred thirty-six thousand, six hundred fifty-one".