21317447 has 2 divisors, whose sum is σ = 21317448. Its totient is φ = 21317446.

The previous prime is 21317441. The next prime is 21317479. The reversal of 21317447 is 74471312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21317447 - 2²⁴ = 4540231 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21317441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10658723 + 10658724.

It is an arithmetic number, because the mean of its divisors is an integer number (10658724).

Almost surely, 2^21317447 is an apocalyptic number.

21317447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21317447 is an equidigital number, since it uses as much as digits as its factorization.

21317447 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4704, while the sum is 29.

The square root of 21317447 is about 4617.0820872062. The cubic root of 21317447 is about 277.2756490925.

Adding to 21317447 its reverse (74471312), we get a palindrome (95788759).

The spelling of 21317447 in words is "twenty-one million, three hundred seventeen thousand, four hundred forty-seven".