129721601 has 4 divisors (see below), whose sum is σ = 130668612. Its totient is φ = 128774592.

The previous prime is 129721591. The next prime is 129721609. The reversal of 129721601 is 106127921.

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 113529025 + 16192576 = 10655^2 + 4024^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-129721601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (129721609) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 473300 + ... + 473573.

It is an arithmetic number, because the mean of its divisors is an integer number (32667153).

Almost surely, 2^129721601 is an apocalyptic number.

It is an amenable number.

129721601 is a deficient number, since it is larger than the sum of its proper divisors (947011).

129721601 is an equidigital number, since it uses as much as digits as its factorization.

129721601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 947010.

The product of its (nonzero) digits is 1512, while the sum is 29.

The square root of 129721601 is about 11389.5391039322. The cubic root of 129721601 is about 506.2178247905.

The spelling of 129721601 in words is "one hundred twenty-nine million, seven hundred twenty-one thousand, six hundred one".