129424721 has 4 divisors (see below), whose sum is σ = 133599744. Its totient is φ = 125249700.

The previous prime is 129424717. The next prime is 129424759. The reversal of 129424721 is 127424921.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 127424921 = 13 ⋅9801917.

It is a cyclic number.

It is not a de Polignac number, because 129424721 - 2² = 129424717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (129420721) 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, 2087465 + ... + 2087526.

It is an arithmetic number, because the mean of its divisors is an integer number (33399936).

Almost surely, 2^129424721 is an apocalyptic number.

It is an amenable number.

129424721 is a deficient number, since it is larger than the sum of its proper divisors (4175023).

129424721 is an equidigital number, since it uses as much as digits as its factorization.

129424721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4175022.

The product of its digits is 8064, while the sum is 32.

The square root of 129424721 is about 11376.4986265547. The cubic root of 129424721 is about 505.8313542246.

The spelling of 129424721 in words is "one hundred twenty-nine million, four hundred twenty-four thousand, seven hundred twenty-one".