21005275 has 12 divisors (see below), whose sum is σ = 26226000. Its totient is φ = 16688480.

The previous prime is 21005269. The next prime is 21005291. The reversal of 21005275 is 57250012.

It is a de Polignac number, because none of the positive numbers 2^k-21005275 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 906 + ... + 6544.

It is an arithmetic number, because the mean of its divisors is an integer number (2185500).

Almost surely, 2^21005275 is an apocalyptic number.

21005275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21005275 is a deficient number, since it is larger than the sum of its proper divisors (5220725).

21005275 is a wasteful number, since it uses less digits than its factorization.

21005275 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5798 (or 5793 counting only the distinct ones).

The product of its (nonzero) digits is 700, while the sum is 22.

The square root of 21005275 is about 4583.1512085027. The cubic root of 21005275 is about 275.9155162201.

Adding to 21005275 its reverse (57250012), we get a palindrome (78255287).

The spelling of 21005275 in words is "twenty-one million, five thousand, two hundred seventy-five".