21445247 has 2 divisors, whose sum is σ = 21445248. Its totient is φ = 21445246.

The previous prime is 21445217. The next prime is 21445327. The reversal of 21445247 is 74254412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21445247 - 2⁶ = 21445183 is a prime.

It is a Chen prime.

It is equal to p_1356329 and since 21445247 and 1356329 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21445217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10722623 + 10722624.

It is an arithmetic number, because the mean of its divisors is an integer number (10722624).

Almost surely, 2^21445247 is an apocalyptic number.

21445247 is a deficient number, since it is larger than the sum of its proper divisors (1).

21445247 is an equidigital number, since it uses as much as digits as its factorization.

21445247 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8960, while the sum is 29.

The square root of 21445247 is about 4630.9013161587. The cubic root of 21445247 is about 277.8286429105.

Adding to 21445247 its reverse (74254412), we get a palindrome (95699659).

The spelling of 21445247 in words is "twenty-one million, four hundred forty-five thousand, two hundred forty-seven".