129721261 has 4 divisors (see below), whose sum is σ = 129902400. Its totient is φ = 129540124.

The previous prime is 129721243. The next prime is 129721289. The reversal of 129721261 is 162127921.

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.

It is a cyclic number.

It is not a de Polignac number, because 129721261 - 2⁷ = 129721133 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 (129721201) 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, 89491 + ... + 90928.

It is an arithmetic number, because the mean of its divisors is an integer number (32475600).

Almost surely, 2^129721261 is an apocalyptic number.

It is an amenable number.

129721261 is a deficient number, since it is larger than the sum of its proper divisors (181139).

129721261 is an equidigital number, since it uses as much as digits as its factorization.

129721261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181138.

The product of its digits is 3024, while the sum is 31.

The square root of 129721261 is about 11389.5241779453. The cubic root of 129721261 is about 506.2173825248.

The spelling of 129721261 in words is "one hundred twenty-nine million, seven hundred twenty-one thousand, two hundred sixty-one".