21752240 has 20 divisors (see below), whose sum is σ = 50574144. Its totient is φ = 8700864.

The previous prime is 21752239. The next prime is 21752243. The reversal of 21752240 is 4225712.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (21752243) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 135872 + ... + 136031.

Almost surely, 2^21752240 is an apocalyptic number.

21752240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21752240 is an abundant number, since it is smaller than the sum of its proper divisors (28821904).

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

21752240 is a wasteful number, since it uses less digits than its factorization.

21752240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 271916 (or 271910 counting only the distinct ones).

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

The square root of 21752240 is about 4663.9296735693. The cubic root of 21752240 is about 279.1480909399.

Adding to 21752240 its reverse (4225712), we get a palindrome (25977952).

The spelling of 21752240 in words is "twenty-one million, seven hundred fifty-two thousand, two hundred forty".