21008436 has 36 divisors (see below), whose sum is σ = 50323392. Its totient is φ = 6818304.

The previous prime is 21008423. The next prime is 21008459. The reversal of 21008436 is 63480012.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 108756 + ... + 108948.

It is an arithmetic number, because the mean of its divisors is an integer number (1397872).

Almost surely, 2^21008436 is an apocalyptic number.

It is an amenable number.

21008436 is an abundant number, since it is smaller than the sum of its proper divisors (29314956).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21008436 is a wasteful number, since it uses less digits than its factorization.

21008436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 440 (or 245 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21008436 is about 4583.4960455966. The cubic root of 21008436 is about 275.9293560008.

Adding to 21008436 its reverse (63480012), we get a palindrome (84488448).

The spelling of 21008436 in words is "twenty-one million, eight thousand, four hundred thirty-six".