129386821 has 2 divisors, whose sum is σ = 129386822. Its totient is φ = 129386820.

The previous prime is 129386819. The next prime is 129386863. The reversal of 129386821 is 128683921.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 114254721 + 15132100 = 10689^2 + 3890^2 .

It is an emirp because it is prime and its reverse (128683921) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 129386821 - 2¹ = 129386819 is a prime.

Together with 129386819, 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 (129386801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64693410 + 64693411.

It is an arithmetic number, because the mean of its divisors is an integer number (64693411).

Almost surely, 2^129386821 is an apocalyptic number.

It is an amenable number.

129386821 is a deficient number, since it is larger than the sum of its proper divisors (1).

129386821 is an equidigital number, since it uses as much as digits as its factorization.

129386821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41472, while the sum is 40.

The square root of 129386821 is about 11374.8327899798. The cubic root of 129386821 is about 505.7819744776.

The spelling of 129386821 in words is "one hundred twenty-nine million, three hundred eighty-six thousand, eight hundred twenty-one".