21236040 has 192 divisors, whose sum is σ = 82454400. Its totient is φ = 4762368.

The previous prime is 21236021. The next prime is 21236041. The reversal of 21236040 is 4063212.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21236041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 400654 + ... + 400706.

It is an arithmetic number, because the mean of its divisors is an integer number (429450).

Almost surely, 2^21236040 is an apocalyptic number.

21236040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21236040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41227200).

21236040 is an abundant number, since it is smaller than the sum of its proper divisors (61218360).

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

21236040 is a wasteful number, since it uses less digits than its factorization.

21236040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133 (or 70 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 21236040 is about 4608.2578052882. The cubic root of 21236040 is about 276.9222457240.

Adding to 21236040 its reverse (4063212), we get a palindrome (25299252).

The spelling of 21236040 in words is "twenty-one million, two hundred thirty-six thousand, forty".