21236742 has 48 divisors (see below), whose sum is σ = 49048272. Its totient is φ = 6881760.

The previous prime is 21236731. The next prime is 21236749. The reversal of 21236742 is 24763212.

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 (21236749) 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 23 ways as a sum of consecutive naturals, for example, 17392 + ... + 18572.

It is an arithmetic number, because the mean of its divisors is an integer number (1021839).

Almost surely, 2^21236742 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21236742, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24524136).

21236742 is an abundant number, since it is smaller than the sum of its proper divisors (27811530).

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

21236742 is a wasteful number, since it uses less digits than its factorization.

21236742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1235 (or 1223 counting only the distinct ones).

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

The square root of 21236742 is about 4608.3339722724. Note that the first 3 decimals coincide. The cubic root of 21236742 is about 276.9252970976.

Adding to 21236742 its reverse (24763212), we get a palindrome (45999954).

The spelling of 21236742 in words is "twenty-one million, two hundred thirty-six thousand, seven hundred forty-two".