21142240 has 96 divisors (see below), whose sum is σ = 58544640. Its totient is φ = 7064064.

The previous prime is 21142223. The next prime is 21142243. The reversal of 21142240 is 4224112.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21142243) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 47941 + ... + 48379.

It is an arithmetic number, because the mean of its divisors is an integer number (609840).

Almost surely, 2^21142240 is an apocalyptic number.

21142240 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 21142240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29272320).

21142240 is an abundant number, since it is smaller than the sum of its proper divisors (37402400).

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

21142240 is a wasteful number, since it uses less digits than its factorization.

21142240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 504 (or 496 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 16.

The square root of 21142240 is about 4598.0691599844. The cubic root of 21142240 is about 276.5139202978.

Adding to 21142240 its reverse (4224112), we get a palindrome (25366352).

The spelling of 21142240 in words is "twenty-one million, one hundred forty-two thousand, two hundred forty".