21042775 has 12 divisors (see below), whose sum is σ = 28100632. Its totient is φ = 15539040.

The previous prime is 21042739. The next prime is 21042803. The reversal of 21042775 is 57724012.

It is not a de Polignac number, because 21042775 - 2⁷ = 21042647 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 32049 + ... + 32698.

Almost surely, 2^21042775 is an apocalyptic number.

21042775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21042775 is a deficient number, since it is larger than the sum of its proper divisors (7057857).

21042775 is a wasteful number, since it uses less digits than its factorization.

21042775 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64770 (or 64765 counting only the distinct ones).

The product of its (nonzero) digits is 3920, while the sum is 28.

The square root of 21042775 is about 4587.2404558732. The cubic root of 21042775 is about 276.0796127891.

Adding to 21042775 its reverse (57724012), we get a palindrome (78766787).

The spelling of 21042775 in words is "twenty-one million, forty-two thousand, seven hundred seventy-five".