21242736 has 100 divisors (see below), whose sum is σ = 63286872. Its totient is φ = 6873984.

The previous prime is 21242729. The next prime is 21242747. The reversal of 21242736 is 63724212.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 47731 + ... + 48173.

Almost surely, 2^21242736 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 21242736, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31643436).

21242736 is an abundant number, since it is smaller than the sum of its proper divisors (42044136).

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

21242736 is a wasteful number, since it uses less digits than its factorization.

21242736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 500 (or 485 counting only the distinct ones).

The product of its digits is 4032, while the sum is 27.

The square root of 21242736 is about 4608.9842698799. The cubic root of 21242736 is about 276.9513483957.

Adding to 21242736 its reverse (63724212), we get a palindrome (84966948).

The spelling of 21242736 in words is "twenty-one million, two hundred forty-two thousand, seven hundred thirty-six".