21427440 has 160 divisors (see below), whose sum is σ = 72376320. Its totient is φ = 5225472.

The previous prime is 21427381. The next prime is 21427447. The reversal of 21427440 is 4472412.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21427440.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21427447) 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 31 ways as a sum of consecutive naturals, for example, 168657 + ... + 168783.

It is an arithmetic number, because the mean of its divisors is an integer number (452352).

Almost surely, 2^21427440 is an apocalyptic number.

21427440 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 21427440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36188160).

21427440 is an abundant number, since it is smaller than the sum of its proper divisors (50948880).

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

21427440 is a wasteful number, since it uses less digits than its factorization.

21427440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 199 (or 193 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 24.

The square root of 21427440 is about 4628.9782889964. The cubic root of 21427440 is about 277.7517235415.

Adding to 21427440 its reverse (4472412), we get a palindrome (25899852).

The spelling of 21427440 in words is "twenty-one million, four hundred twenty-seven thousand, four hundred forty".