21281752 has 8 divisors (see below), whose sum is σ = 39903300. Its totient is φ = 10640872.

The previous prime is 21281719. The next prime is 21281783. The reversal of 21281752 is 25718212.

It is a tau number, because it is divible by the number of its divisors (8).

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21281752.

It is a congruent number.

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 1330102 + ... + 1330117.

Almost surely, 2^21281752 is an apocalyptic number.

It is an amenable number.

21281752 is a deficient number, since it is larger than the sum of its proper divisors (18621548).

21281752 is a wasteful number, since it uses less digits than its factorization.

21281752 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2660225 (or 2660221 counting only the distinct ones).

The product of its digits is 2240, while the sum is 28.

The square root of 21281752 is about 4613.2149310432. The cubic root of 21281752 is about 277.1208012247.

Adding to 21281752 its reverse (25718212), we get a palindrome (46999964).

The spelling of 21281752 in words is "twenty-one million, two hundred eighty-one thousand, seven hundred fifty-two".