129072821 has 2 divisors, whose sum is σ = 129072822. Its totient is φ = 129072820.

The previous prime is 129072791. The next prime is 129072829. The reversal of 129072821 is 128270921.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 128368900 + 703921 = 11330^2 + 839^2 .

It is an emirp because it is prime and its reverse (128270921) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 129072821 - 2¹⁴ = 129056437 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (129072829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64536410 + 64536411.

It is an arithmetic number, because the mean of its divisors is an integer number (64536411).

Almost surely, 2^129072821 is an apocalyptic number.

It is an amenable number.

129072821 is a deficient number, since it is larger than the sum of its proper divisors (1).

129072821 is an equidigital number, since it uses as much as digits as its factorization.

129072821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 129072821 is about 11361.0220050839. The cubic root of 129072821 is about 505.3724938595.

The spelling of 129072821 in words is "one hundred twenty-nine million, seventy-two thousand, eight hundred twenty-one".