21004547 has 2 divisors, whose sum is σ = 21004548. Its totient is φ = 21004546.

The previous prime is 21004541. The next prime is 21004549. The reversal of 21004547 is 74540012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21004547 is a prime.

Together with 21004549, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21004541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502273 + 10502274.

It is an arithmetic number, because the mean of its divisors is an integer number (10502274).

Almost surely, 2^21004547 is an apocalyptic number.

21004547 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004547 is an equidigital number, since it uses as much as digits as its factorization.

21004547 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21004547 is about 4583.0717864768. The cubic root of 21004547 is about 275.9123286269.

Adding to 21004547 its reverse (74540012), we get a palindrome (95544559).

The spelling of 21004547 in words is "twenty-one million, four thousand, five hundred forty-seven".