129730721 has 2 divisors, whose sum is σ = 129730722. Its totient is φ = 129730720.

The previous prime is 129730609. The next prime is 129730751. The reversal of 129730721 is 127037921.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 122766400 + 6964321 = 11080^2 + 2639^2 .

It is an emirp because it is prime and its reverse (127037921) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 129730721 - 2¹⁰ = 129729697 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is equal to p_7363850 and since 129730721 and 7363850 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 (129730751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64865360 + 64865361.

It is an arithmetic number, because the mean of its divisors is an integer number (64865361).

Almost surely, 2^129730721 is an apocalyptic number.

It is an amenable number.

129730721 is a deficient number, since it is larger than the sum of its proper divisors (1).

129730721 is an equidigital number, since it uses as much as digits as its factorization.

129730721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5292, while the sum is 32.

The square root of 129730721 is about 11389.9394642816. The cubic root of 129730721 is about 506.2296876268.

The spelling of 129730721 in words is "one hundred twenty-nine million, seven hundred thirty thousand, seven hundred twenty-one".