21072240 has 240 divisors, whose sum is σ = 83798208. Its totient is φ = 4644864.

The previous prime is 21072239. The next prime is 21072251. The reversal of 21072240 is 4227012.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 186424 + ... + 186536.

Almost surely, 2^21072240 is an apocalyptic number.

21072240 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 21072240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41899104).

21072240 is an abundant number, since it is smaller than the sum of its proper divisors (62725968).

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

21072240 is a wasteful number, since it uses less digits than its factorization.

21072240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 176 (or 167 counting only the distinct ones).

The product of its (nonzero) digits is 224, while the sum is 18.

The square root of 21072240 is about 4590.4509582393. The cubic root of 21072240 is about 276.2084122131.

Adding to 21072240 its reverse (4227012), we get a palindrome (25299252).

It can be divided in two parts, 21072 and 240, that added together give a palindrome (21312).

The spelling of 21072240 in words is "twenty-one million, seventy-two thousand, two hundred forty".