21354440 has 64 divisors (see below), whose sum is σ = 51030000. Its totient is φ = 8028160.

The previous prime is 21354433. The next prime is 21354449. The reversal of 21354440 is 4445312.

It can be written as a sum of positive squares in 8 ways, for example, as 4919524 + 16434916 = 2218^2 + 4054^2 .

It is not an unprimeable number, because it can be changed into a prime (21354449) 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 15 ways as a sum of consecutive naturals, for example, 47336 + ... + 47784.

Almost surely, 2^21354440 is an apocalyptic number.

21354440 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 21354440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25515000).

21354440 is an abundant number, since it is smaller than the sum of its proper divisors (29675560).

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

21354440 is a wasteful number, since it uses less digits than its factorization.

21354440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 530 (or 526 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 23.

The square root of 21354440 is about 4621.0864523400. The cubic root of 21354440 is about 277.4359455002.

Adding to 21354440 its reverse (4445312), we get a palindrome (25799752).

The spelling of 21354440 in words is "twenty-one million, three hundred fifty-four thousand, four hundred forty".