21002129 has 2 divisors, whose sum is σ = 21002130. Its totient is φ = 21002128.

The previous prime is 21002101. The next prime is 21002203. The reversal of 21002129 is 92120012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17833729 + 3168400 = 4223^2 + 1780^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21002129 is a prime.

It is a Chen prime.

It is equal to p_1330073 and since 21002129 and 1330073 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21002329) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501064 + 10501065.

It is an arithmetic number, because the mean of its divisors is an integer number (10501065).

Almost surely, 2^21002129 is an apocalyptic number.

It is an amenable number.

21002129 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002129 is an equidigital number, since it uses as much as digits as its factorization.

21002129 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 21002129 is about 4582.8079820128. The cubic root of 21002129 is about 275.9017407351.

The spelling of 21002129 in words is "twenty-one million, two thousand, one hundred twenty-nine".