21011836 has 12 divisors (see below), whose sum is σ = 36871912. Its totient is φ = 10477008.

The previous prime is 21011807. The next prime is 21011839. The reversal of 21011836 is 63811012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011839) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5550 + ... + 8533.

Almost surely, 2^21011836 is an apocalyptic number.

It is an amenable number.

21011836 is a deficient number, since it is larger than the sum of its proper divisors (15860076).

21011836 is a wasteful number, since it uses less digits than its factorization.

21011836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14460 (or 14458 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 21011836 is about 4583.8669265152. The cubic root of 21011836 is about 275.9442406437.

Adding to 21011836 its reverse (63811012), we get a palindrome (84822848).

The spelling of 21011836 in words is "twenty-one million, eleven thousand, eight hundred thirty-six".