21718447 has 2 divisors, whose sum is σ = 21718448. Its totient is φ = 21718446.

The previous prime is 21718439. The next prime is 21718451. The reversal of 21718447 is 74481712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21718447 - 2³ = 21718439 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21718427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10859223 + 10859224.

It is an arithmetic number, because the mean of its divisors is an integer number (10859224).

Almost surely, 2^21718447 is an apocalyptic number.

21718447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21718447 is an equidigital number, since it uses as much as digits as its factorization.

21718447 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12544, while the sum is 34.

The square root of 21718447 is about 4660.3054620915. The cubic root of 21718447 is about 279.0034600017.

The spelling of 21718447 in words is "twenty-one million, seven hundred eighteen thousand, four hundred forty-seven".