21042071 has 4 divisors (see below), whose sum is σ = 21063144. Its totient is φ = 21021000.

The previous prime is 21042059. The next prime is 21042089. The reversal of 21042071 is 17024012.

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

It is a cyclic number.

It is not a de Polignac number, because 21042071 - 2¹⁰ = 21041047 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21042971) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 8960 + ... + 11061.

It is an arithmetic number, because the mean of its divisors is an integer number (5265786).

Almost surely, 2^21042071 is an apocalyptic number.

21042071 is a deficient number, since it is larger than the sum of its proper divisors (21073).

21042071 is a wasteful number, since it uses less digits than its factorization.

21042071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21072.

The product of its (nonzero) digits is 112, while the sum is 17.

The square root of 21042071 is about 4587.1637206448. The cubic root of 21042071 is about 276.0765339459.

Adding to 21042071 its reverse (17024012), we get a palindrome (38066083).

The spelling of 21042071 in words is "twenty-one million, forty-two thousand, seventy-one".