21444251 has 2 divisors, whose sum is σ = 21444252. Its totient is φ = 21444250.

The previous prime is 21444239. The next prime is 21444263. The reversal of 21444251 is 15244412.

It is a balanced prime because it is at equal distance from previous prime (21444239) and next prime (21444263).

It is a cyclic number.

It is not a de Polignac number, because 21444251 - 2⁶ = 21444187 is a prime.

It is not a weakly prime, because it can be changed into another prime (21444751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10722125 + 10722126.

It is an arithmetic number, because the mean of its divisors is an integer number (10722126).

Almost surely, 2^21444251 is an apocalyptic number.

21444251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21444251 is an equidigital number, since it uses as much as digits as its factorization.

21444251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1280, while the sum is 23.

The square root of 21444251 is about 4630.7937764491. The cubic root of 21444251 is about 277.8243416992.

Adding to 21444251 its reverse (15244412), we get a palindrome (36688663).

The spelling of 21444251 in words is "twenty-one million, four hundred forty-four thousand, two hundred fifty-one".