129730021 has 4 divisors (see below), whose sum is σ = 134203500. Its totient is φ = 125256544.

The previous prime is 129729991. The next prime is 129730033. The reversal of 129730021 is 120037921.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 50608996 + 79121025 = 7114^2 + 8895^2 .

It is a cyclic number.

It is not a de Polignac number, because 129730021 - 2¹³ = 129721829 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (129730091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2236696 + ... + 2236753.

It is an arithmetic number, because the mean of its divisors is an integer number (33550875).

Almost surely, 2^129730021 is an apocalyptic number.

It is an amenable number.

129730021 is a deficient number, since it is larger than the sum of its proper divisors (4473479).

129730021 is an equidigital number, since it uses as much as digits as its factorization.

129730021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4473478.

The product of its (nonzero) digits is 756, while the sum is 25.

The square root of 129730021 is about 11389.9087353675. The cubic root of 129730021 is about 506.2287771218.

Adding to 129730021 its reverse (120037921), we get a palindrome (249767942).

It can be divided in two parts, 1297300 and 21, that added together give a square (1297321 = 1139²).

The spelling of 129730021 in words is "one hundred twenty-nine million, seven hundred thirty thousand, twenty-one".