21572240 has 40 divisors (see below), whose sum is σ = 51330048. Its totient is φ = 8426880.

The previous prime is 21572237. The next prime is 21572251. The reversal of 21572240 is 4227512.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

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, 305 + ... + 6575.

Almost surely, 2^21572240 is an apocalyptic number.

21572240 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 21572240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25665024).

21572240 is an abundant number, since it is smaller than the sum of its proper divisors (29757808).

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

21572240 is a wasteful number, since it uses less digits than its factorization.

21572240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6327 (or 6321 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21572240 is about 4644.5925547888. The cubic root of 21572240 is about 278.3759728460.

Adding to 21572240 its reverse (4227512), we get a palindrome (25799752).

It can be divided in two parts, 21572 and 240, that added together give a palindrome (21812).

The spelling of 21572240 in words is "twenty-one million, five hundred seventy-two thousand, two hundred forty".