21045236 has 24 divisors (see below), whose sum is σ = 39355680. Its totient is φ = 9817632.

The previous prime is 21045229. The next prime is 21045239. The reversal of 21045236 is 63254012.

21045236 = 294² + 295² + ... + 445².

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21045239) 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 in 7 ways as a sum of consecutive naturals, for example, 3026 + ... + 7158.

It is an arithmetic number, because the mean of its divisors is an integer number (1639820).

Almost surely, 2^21045236 is an apocalyptic number.

It is an amenable number.

21045236 is a deficient number, since it is larger than the sum of its proper divisors (18310444).

21045236 is a wasteful number, since it uses less digits than its factorization.

21045236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4223 (or 4221 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 21045236 is about 4587.5086920899. The cubic root of 21045236 is about 276.0903750807.

Adding to 21045236 its reverse (63254012), we get a palindrome (84299248).

The spelling of 21045236 in words is "twenty-one million, forty-five thousand, two hundred thirty-six".