21641240 has 32 divisors (see below), whose sum is σ = 49248000. Its totient is φ = 8557824.

The previous prime is 21641239. The next prime is 21641267. The reversal of 21641240 is 4214612.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 521 + ... + 6599.

It is an arithmetic number, because the mean of its divisors is an integer number (1539000).

Almost surely, 2^21641240 is an apocalyptic number.

21641240 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 21641240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24624000).

21641240 is an abundant number, since it is smaller than the sum of its proper divisors (27606760).

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

21641240 is a wasteful number, since it uses less digits than its factorization.

21641240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6179 (or 6175 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 21641240 is about 4652.0146173459. The cubic root of 21641240 is about 278.6724572664.

Adding to 21641240 its reverse (4214612), we get a palindrome (25855852).

The spelling of 21641240 in words is "twenty-one million, six hundred forty-one thousand, two hundred forty".