21052121 has 2 divisors, whose sum is σ = 21052122. Its totient is φ = 21052120.

The previous prime is 21052117. The next prime is 21052127. The reversal of 21052121 is 12125012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14478025 + 6574096 = 3805^2 + 2564^2 .

It is a cyclic number.

It is not a de Polignac number, because 21052121 - 2² = 21052117 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21052096 and 21052105.

It is not a weakly prime, because it can be changed into another prime (21052127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10526060 + 10526061.

It is an arithmetic number, because the mean of its divisors is an integer number (10526061).

Almost surely, 2^21052121 is an apocalyptic number.

It is an amenable number.

21052121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21052121 is an equidigital number, since it uses as much as digits as its factorization.

21052121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21052121 is about 4588.2590380230. The cubic root of 21052121 is about 276.1204796766.

Adding to 21052121 its reverse (12125012), we get a palindrome (33177133).

The spelling of 21052121 in words is "twenty-one million, fifty-two thousand, one hundred twenty-one".