21456738 has 40 divisors (see below), whose sum is σ = 50616720. Its totient is φ = 6774840.

The previous prime is 21456731. The next prime is 21456739. The reversal of 21456738 is 83765412.

It is a nialpdrome in base 9.

It is not an unprimeable number, because it can be changed into a prime (21456731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 408 + ... + 6563.

It is an arithmetic number, because the mean of its divisors is an integer number (1265418).

Almost surely, 2^21456738 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21456738, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25308360).

21456738 is an abundant number, since it is smaller than the sum of its proper divisors (29159982).

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

21456738 is a wasteful number, since it uses less digits than its factorization.

21456738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7004 (or 6995 counting only the distinct ones).

The product of its digits is 40320, while the sum is 36.

The square root of 21456738 is about 4632.1418372066. The cubic root of 21456738 is about 277.8782569949.

The spelling of 21456738 in words is "twenty-one million, four hundred fifty-six thousand, seven hundred thirty-eight".