21000071 has 4 divisors (see below), whose sum is σ = 21010200. Its totient is φ = 20989944.

The previous prime is 21000059. The next prime is 21000097. The reversal of 21000071 is 17000012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21000071 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 (21000041) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 701 + ... + 6518.

It is an arithmetic number, because the mean of its divisors is an integer number (5252550).

Almost surely, 2^21000071 is an apocalyptic number.

21000071 is a deficient number, since it is larger than the sum of its proper divisors (10129).

21000071 is an equidigital number, since it uses as much as digits as its factorization.

21000071 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10128.

The product of its (nonzero) digits is 14, while the sum is 11.

The square root of 21000071 is about 4582.5834416844. The cubic root of 21000071 is about 275.8927285641.

Adding to 21000071 its reverse (17000012), we get a palindrome (38000083).

The spelling of 21000071 in words is "twenty-one million, seventy-one", and thus it is an aban number and an uban number.