21541240 has 64 divisors (see below), whose sum is σ = 55987200. Its totient is φ = 7306368.

The previous prime is 21541217. The next prime is 21541241. The reversal of 21541240 is 4214512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21541241) 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 15 ways as a sum of consecutive naturals, for example, 29601 + ... + 30319.

It is an arithmetic number, because the mean of its divisors is an integer number (874800).

Almost surely, 2^21541240 is an apocalyptic number.

21541240 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 21541240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27993600).

21541240 is an abundant number, since it is smaller than the sum of its proper divisors (34445960).

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

21541240 is a wasteful number, since it uses less digits than its factorization.

21541240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844 (or 840 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 21541240 is about 4641.2541408546. The cubic root of 21541240 is about 278.2425638575.

Adding to 21541240 its reverse (4214512), we get a palindrome (25755752).

The spelling of 21541240 in words is "twenty-one million, five hundred forty-one thousand, two hundred forty".