21418247 has 2 divisors, whose sum is σ = 21418248. Its totient is φ = 21418246.

The previous prime is 21418237. The next prime is 21418253. The reversal of 21418247 is 74281412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21418247 - 2⁴ = 21418231 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21418207) 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, 10709123 + 10709124.

It is an arithmetic number, because the mean of its divisors is an integer number (10709124).

Almost surely, 2^21418247 is an apocalyptic number.

21418247 is a deficient number, since it is larger than the sum of its proper divisors (1).

21418247 is an equidigital number, since it uses as much as digits as its factorization.

21418247 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3584, while the sum is 29.

The square root of 21418247 is about 4627.9851987663. The cubic root of 21418247 is about 277.7119966486.

Adding to 21418247 its reverse (74281412), we get a palindrome (95699659).

The spelling of 21418247 in words is "twenty-one million, four hundred eighteen thousand, two hundred forty-seven".