21445217 has 2 divisors, whose sum is σ = 21445218. Its totient is φ = 21445216.

The previous prime is 21445201. The next prime is 21445247. The reversal of 21445217 is 71254412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11262736 + 10182481 = 3356^2 + 3191^2 .

It is a cyclic number.

It is not a de Polignac number, because 21445217 - 2⁴ = 21445201 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21445247) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10722608 + 10722609.

It is an arithmetic number, because the mean of its divisors is an integer number (10722609).

Almost surely, 2^21445217 is an apocalyptic number.

It is an amenable number.

21445217 is a deficient number, since it is larger than the sum of its proper divisors (1).

21445217 is an equidigital number, since it uses as much as digits as its factorization.

21445217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2240, while the sum is 26.

The square root of 21445217 is about 4630.8980770473. The cubic root of 21445217 is about 277.8285133579.

Adding to 21445217 its reverse (71254412), we get a palindrome (92699629).

The spelling of 21445217 in words is "twenty-one million, four hundred forty-five thousand, two hundred seventeen".