21245755 has 4 divisors (see below), whose sum is σ = 25494912. Its totient is φ = 16996600.

The previous prime is 21245753. The next prime is 21245771. The reversal of 21245755 is 55754212.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21245755 - 2¹ = 21245753 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21245753) 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, 2124571 + ... + 2124580.

It is an arithmetic number, because the mean of its divisors is an integer number (6373728).

Almost surely, 2^21245755 is an apocalyptic number.

21245755 is a deficient number, since it is larger than the sum of its proper divisors (4249157).

21245755 is an equidigital number, since it uses as much as digits as its factorization.

21245755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4249156.

The product of its digits is 14000, while the sum is 31.

The square root of 21245755 is about 4609.3117707528. The cubic root of 21245755 is about 276.9644678061.

Adding to 21245755 its reverse (55754212), we get a palindrome (76999967).

The spelling of 21245755 in words is "twenty-one million, two hundred forty-five thousand, seven hundred fifty-five".