129211021 has 2 divisors, whose sum is σ = 129211022. Its totient is φ = 129211020.

The previous prime is 129211009. The next prime is 129211051. The reversal of 129211021 is 120112921.

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., 124322500 + 4888521 = 11150^2 + 2211^2 .

It is a cyclic number.

It is not a de Polignac number, because 129211021 - 2⁵ = 129210989 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 129211021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (129211051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64605510 + 64605511.

It is an arithmetic number, because the mean of its divisors is an integer number (64605511).

Almost surely, 2^129211021 is an apocalyptic number.

It is an amenable number.

129211021 is a deficient number, since it is larger than the sum of its proper divisors (1).

129211021 is an equidigital number, since it uses as much as digits as its factorization.

129211021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 19.

The square root of 129211021 is about 11367.1025771742. The cubic root of 129211021 is about 505.5527992246.

Adding to 129211021 its reverse (120112921), we get a palindrome (249323942).

The spelling of 129211021 in words is "one hundred twenty-nine million, two hundred eleven thousand, twenty-one".