21044557 has 2 divisors, whose sum is σ = 21044558. Its totient is φ = 21044556.

The previous prime is 21044531. The next prime is 21044581. The reversal of 21044557 is 75544012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17147881 + 3896676 = 4141^2 + 1974^2 .

It is a cyclic number.

It is not a de Polignac number, because 21044557 - 2¹⁵ = 21011789 is a prime.

It is a congruent number.

It is a weakly prime.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10522278 + 10522279.

It is an arithmetic number, because the mean of its divisors is an integer number (10522279).

Almost surely, 2^21044557 is an apocalyptic number.

It is an amenable number.

21044557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21044557 is an equidigital number, since it uses as much as digits as its factorization.

21044557 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 5600, while the sum is 28.

The square root of 21044557 is about 4587.4346861836. The cubic root of 21044557 is about 276.0874058041.

Adding to 21044557 its reverse (75544012), we get a palindrome (96588569).

The spelling of 21044557 in words is "twenty-one million, forty-four thousand, five hundred fifty-seven".