129721281 has 8 divisors (see below), whose sum is σ = 175045920. Its totient is φ = 85438752.

The previous prime is 129721243. The next prime is 129721289. The reversal of 129721281 is 182127921.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 129721281 - 2¹⁰ = 129720257 is a prime.

It is a super-2 number, since 2×129721281² = 33655221488561922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (129721289) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 260236 + ... + 260733.

It is an arithmetic number, because the mean of its divisors is an integer number (21880740).

Almost surely, 2^129721281 is an apocalyptic number.

It is an amenable number.

129721281 is a deficient number, since it is larger than the sum of its proper divisors (45324639).

129721281 is an equidigital number, since it uses as much as digits as its factorization.

129721281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 521055.

The product of its digits is 4032, while the sum is 33.

The square root of 129721281 is about 11389.5250559450. The cubic root of 129721281 is about 506.2174085405.

It can be divided in two parts, 1297 and 21281, that added together give a triangular number (22578 = T₂₁₂).

The spelling of 129721281 in words is "one hundred twenty-nine million, seven hundred twenty-one thousand, two hundred eighty-one".