21006547 has 2 divisors, whose sum is σ = 21006548. Its totient is φ = 21006546.

The previous prime is 21006523. The next prime is 21006551. The reversal of 21006547 is 74560012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21006547 - 2¹¹ = 21004499 is a prime.

It is not a weakly prime, because it can be changed into another prime (21006247) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10503273 + 10503274.

It is an arithmetic number, because the mean of its divisors is an integer number (10503274).

Almost surely, 2^21006547 is an apocalyptic number.

21006547 is a deficient number, since it is larger than the sum of its proper divisors (1).

21006547 is an equidigital number, since it uses as much as digits as its factorization.

21006547 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 21006547 is about 4583.2899755525. The cubic root of 21006547 is about 275.9210855743.

Adding to 21006547 its reverse (74560012), we get a palindrome (95566559).

The spelling of 21006547 in words is "twenty-one million, six thousand, five hundred forty-seven".