21115836 has 192 divisors, whose sum is σ = 69672960. Its totient is φ = 5391360.

The previous prime is 21115793. The next prime is 21115837. The reversal of 21115836 is 63851112.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21115837) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 398386 + ... + 398438.

It is an arithmetic number, because the mean of its divisors is an integer number (362880).

Almost surely, 2^21115836 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21115836, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34836480).

21115836 is an abundant number, since it is smaller than the sum of its proper divisors (48557124).

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

21115836 is a wasteful number, since it uses less digits than its factorization.

21115836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 121 (or 113 counting only the distinct ones).

The product of its digits is 1440, while the sum is 27.

The square root of 21115836 is about 4595.1970577985. The cubic root of 21115836 is about 276.3987619696.

Adding to 21115836 its reverse (63851112), we get a palindrome (84966948).

The spelling of 21115836 in words is "twenty-one million, one hundred fifteen thousand, eight hundred thirty-six".