21043536 has 40 divisors (see below), whose sum is σ = 55261344. Its totient is φ = 6898560.

The previous prime is 21043523. The next prime is 21043543. The reversal of 21043536 is 63534012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

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, 666 + ... + 6521.

Almost surely, 2^21043536 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 21043536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27630672).

21043536 is an abundant number, since it is smaller than the sum of its proper divisors (34217808).

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

21043536 is a wasteful number, since it uses less digits than its factorization.

21043536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7259 (or 7253 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 24.

The square root of 21043536 is about 4587.3234025955. The cubic root of 21043536 is about 276.0829408364.

Adding to 21043536 its reverse (63534012), we get a palindrome (84577548).

The spelling of 21043536 in words is "twenty-one million, forty-three thousand, five hundred thirty-six".