21121836 has 24 divisors (see below), whose sum is σ = 49840560. Its totient is φ = 6961152.

The previous prime is 21121813. The next prime is 21121853. The reversal of 21121836 is 63812112.

It is a super-2 number, since 2×21121836² = 892263912021792, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8821 + ... + 10956.

It is an arithmetic number, because the mean of its divisors is an integer number (2076690).

Almost surely, 2^21121836 is an apocalyptic number.

It is an amenable number.

21121836 is an abundant number, since it is smaller than the sum of its proper divisors (28718724).

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

21121836 is a wasteful number, since it uses less digits than its factorization.

21121836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19873 (or 19871 counting only the distinct ones).

The product of its digits is 576, while the sum is 24.

The square root of 21121836 is about 4595.8498669996. The cubic root of 21121836 is about 276.4249387771.

Adding to 21121836 its reverse (63812112), we get a palindrome (84933948).

The spelling of 21121836 in words is "twenty-one million, one hundred twenty-one thousand, eight hundred thirty-six".