21071021 has 2 divisors, whose sum is σ = 21071022. Its totient is φ = 21071020.

The previous prime is 21071009. The next prime is 21071033. The reversal of 21071021 is 12017012.

It is a balanced prime because it is at equal distance from previous prime (21071009) and next prime (21071033).

It can be written as a sum of positive squares in only one way, i.e., 21058921 + 12100 = 4589^2 + 110^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21071021 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21070987 and 21071005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21071221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10535510 + 10535511.

It is an arithmetic number, because the mean of its divisors is an integer number (10535511).

Almost surely, 2^21071021 is an apocalyptic number.

It is an amenable number.

21071021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21071021 is an equidigital number, since it uses as much as digits as its factorization.

21071021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28, while the sum is 14.

The square root of 21071021 is about 4590.3181806929. The cubic root of 21071021 is about 276.2030860186.

Adding to 21071021 its reverse (12017012), we get a palindrome (33088033).

The spelling of 21071021 in words is "twenty-one million, seventy-one thousand, twenty-one".