21212636 has 12 divisors (see below), whose sum is σ = 37242912. Its totient is φ = 10571808.

The previous prime is 21212629. The next prime is 21212641. The reversal of 21212636 is 63621212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7220 + ... + 9723.

It is an arithmetic number, because the mean of its divisors is an integer number (3103576).

Almost surely, 2^21212636 is an apocalyptic number.

It is an amenable number.

21212636 is a deficient number, since it is larger than the sum of its proper divisors (16030276).

21212636 is a wasteful number, since it uses less digits than its factorization.

21212636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17260 (or 17258 counting only the distinct ones).

The product of its digits is 864, while the sum is 23.

The square root of 21212636 is about 4605.7177507963. The cubic root of 21212636 is about 276.8204773684.

Adding to 21212636 its reverse (63621212), we get a palindrome (84833848).

The spelling of 21212636 in words is "twenty-one million, two hundred twelve thousand, six hundred thirty-six".