21040447 has 2 divisors, whose sum is σ = 21040448. Its totient is φ = 21040446.

The previous prime is 21040427. The next prime is 21040463. The reversal of 21040447 is 74404012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21040447 - 2²³ = 12651839 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21040427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10520223 + 10520224.

It is an arithmetic number, because the mean of its divisors is an integer number (10520224).

Almost surely, 2^21040447 is an apocalyptic number.

21040447 is a deficient number, since it is larger than the sum of its proper divisors (1).

21040447 is an equidigital number, since it uses as much as digits as its factorization.

21040447 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 896, while the sum is 22.

The square root of 21040447 is about 4586.9867015286. The cubic root of 21040447 is about 276.0694313525.

Adding to 21040447 its reverse (74404012), we get a palindrome (95444459).

The spelling of 21040447 in words is "twenty-one million, forty thousand, four hundred forty-seven".