21020012129 has 2 divisors, whose sum is σ = 21020012130. Its totient is φ = 21020012128.

The previous prime is 21020012099. The next prime is 21020012161. The reversal of 21020012129 is 92121002012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17616456529 + 3403555600 = 132727^2 + 58340^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020012129 - 2¹² = 21020008033 is a prime.

It is a super-2 number, since 2×21020012129² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21020012129.

It is not a weakly prime, because it can be changed into another prime (21020012329) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510006064 + 10510006065.

It is an arithmetic number, because the mean of its divisors is an integer number (10510006065).

Almost surely, 2^21020012129 is an apocalyptic number.

It is an amenable number.

21020012129 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020012129 is an equidigital number, since it uses as much as digits as its factorization.

21020012129 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 20.

The spelling of 21020012129 in words is "twenty-one billion, twenty million, twelve thousand, one hundred twenty-nine".