21258240 has 112 divisors (see below), whose sum is σ = 68415408. Its totient is φ = 5636096.

The previous prime is 21258199. The next prime is 21258253. The reversal of 21258240 is 4285212.

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 21258240.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 122794 + ... + 122966.

Almost surely, 2^21258240 is an apocalyptic number.

21258240 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 21258240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34207704).

21258240 is an abundant number, since it is smaller than the sum of its proper divisors (47157168).

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

21258240 is an equidigital number, since it uses as much as digits as its factorization.

21258240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207 (or 183 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 24.

The square root of 21258240 is about 4610.6658955079. The cubic root of 21258240 is about 277.0187096105.

The spelling of 21258240 in words is "twenty-one million, two hundred fifty-eight thousand, two hundred forty".