21144436 has 6 divisors (see below), whose sum is σ = 37002770. Its totient is φ = 10572216.

The previous prime is 21144419. The next prime is 21144437. The reversal of 21144436 is 63444112.

It can be written as a sum of positive squares in only one way, i.e., 18011536 + 3132900 = 4244^2 + 1770^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21144436.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21144437) by changing a digit.

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, 2643051 + ... + 2643058.

Almost surely, 2^21144436 is an apocalyptic number.

It is an amenable number.

21144436 is a deficient number, since it is larger than the sum of its proper divisors (15858334).

21144436 is a wasteful number, since it uses less digits than its factorization.

21144436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5286113 (or 5286111 counting only the distinct ones).

The product of its digits is 2304, while the sum is 25.

The square root of 21144436 is about 4598.3079496702. The cubic root of 21144436 is about 276.5234936061.

Adding to 21144436 its reverse (63444112), we get a palindrome (84588548).

The spelling of 21144436 in words is "twenty-one million, one hundred forty-four thousand, four hundred thirty-six".