21249636 has 24 divisors (see below), whose sum is σ = 49902720. Its totient is φ = 7037472.

The previous prime is 21249623. The next prime is 21249637. The reversal of 21249636 is 63694212.

It is a junction number, because it is equal to n+sod(n) for n = 21249597 and 21249606.

It is not an unprimeable number, because it can be changed into a prime (21249637) 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 in 7 ways as a sum of consecutive naturals, for example, 3756 + ... + 7523.

It is an arithmetic number, because the mean of its divisors is an integer number (2079280).

Almost surely, 2^21249636 is an apocalyptic number.

It is an amenable number.

21249636 is an abundant number, since it is smaller than the sum of its proper divisors (28653084).

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

21249636 is a wasteful number, since it uses less digits than its factorization.

21249636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11443 (or 11441 counting only the distinct ones).

The product of its digits is 15552, while the sum is 33.

The square root of 21249636 is about 4609.7327471340. The cubic root of 21249636 is about 276.9813313106.

The spelling of 21249636 in words is "twenty-one million, two hundred forty-nine thousand, six hundred thirty-six".