21227581 has 2 divisors, whose sum is σ = 21227582. Its totient is φ = 21227580.

The previous prime is 21227567. The next prime is 21227599. The reversal of 21227581 is 18572212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14699556 + 6528025 = 3834^2 + 2555^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21227581 is a prime.

It is a super-2 number, since 2×21227581² = 901220390223122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21227501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10613790 + 10613791.

It is an arithmetic number, because the mean of its divisors is an integer number (10613791).

Almost surely, 2^21227581 is an apocalyptic number.

It is an amenable number.

21227581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21227581 is an equidigital number, since it uses as much as digits as its factorization.

21227581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2240, while the sum is 28.

The square root of 21227581 is about 4607.3399049777. The cubic root of 21227581 is about 276.8854718187.

Adding to 21227581 its reverse (18572212), we get a palindrome (39799793).

The spelling of 21227581 in words is "twenty-one million, two hundred twenty-seven thousand, five hundred eighty-one".