21020071 has 4 divisors (see below), whose sum is σ = 21056112. Its totient is φ = 20984032.

The previous prime is 21020059. The next prime is 21020081. The reversal of 21020071 is 17002012.

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 21020071 - 2⁵ = 21020039 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 (21020011) 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, 17131 + ... + 18316.

It is an arithmetic number, because the mean of its divisors is an integer number (5264028).

Almost surely, 2^21020071 is an apocalyptic number.

21020071 is a deficient number, since it is larger than the sum of its proper divisors (36041).

21020071 is an equidigital number, since it uses as much as digits as its factorization.

21020071 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36040.

The product of its (nonzero) digits is 28, while the sum is 13.

The square root of 21020071 is about 4584.7650975813. The cubic root of 21020071 is about 275.9802854713.

Adding to 21020071 its reverse (17002012), we get a palindrome (38022083).

The spelling of 21020071 in words is "twenty-one million, twenty thousand, seventy-one".