21142440 has 192 divisors, whose sum is σ = 79185600. Its totient is φ = 4838400.

The previous prime is 21142439. The next prime is 21142447. The reversal of 21142440 is 4424112.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21142447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 75100 + ... + 75380.

It is an arithmetic number, because the mean of its divisors is an integer number (412425).

Almost surely, 2^21142440 is an apocalyptic number.

21142440 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 21142440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39592800).

21142440 is an abundant number, since it is smaller than the sum of its proper divisors (58043160).

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

21142440 is a wasteful number, since it uses less digits than its factorization.

21142440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328 (or 321 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 21142440 is about 4598.0909081922. The cubic root of 21142440 is about 276.5147922112.

Adding to 21142440 its reverse (4424112), we get a palindrome (25566552).

It can be divided in two parts, 2114 and 2440, that added together give a palindrome (4554).

The spelling of 21142440 in words is "twenty-one million, one hundred forty-two thousand, four hundred forty".