21002101 has 2 divisors, whose sum is σ = 21002102. Its totient is φ = 21002100.

The previous prime is 21002099. The next prime is 21002129. The reversal of 21002101 is 10120012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10595025 + 10407076 = 3255^2 + 3226^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002101 - 2¹ = 21002099 is a prime.

Together with 21002099, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21062101) 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 as a sum of consecutive naturals, namely, 10501050 + 10501051.

It is an arithmetic number, because the mean of its divisors is an integer number (10501051).

Almost surely, 2^21002101 is an apocalyptic number.

It is an amenable number.

21002101 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002101 is an equidigital number, since it uses as much as digits as its factorization.

21002101 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4, while the sum is 7.

The square root of 21002101 is about 4582.8049271161. The cubic root of 21002101 is about 275.9016181245.

Adding to 21002101 its reverse (10120012), we get a palindrome (31122113).

The spelling of 21002101 in words is "twenty-one million, two thousand, one hundred one".