129821905 has 4 divisors (see below), whose sum is σ = 155786292. Its totient is φ = 103857520.

The previous prime is 129821899. The next prime is 129821929. The reversal of 129821905 is 509128921.

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 21641104 + 108180801 = 4652^2 + 10401^2 .

It is not a de Polignac number, because 129821905 - 2¹¹ = 129819857 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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, 12982186 + ... + 12982195.

It is an arithmetic number, because the mean of its divisors is an integer number (38946573).

Almost surely, 2^129821905 is an apocalyptic number.

It is an amenable number.

129821905 is a deficient number, since it is larger than the sum of its proper divisors (25964387).

129821905 is an equidigital number, since it uses as much as digits as its factorization.

129821905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25964386.

The product of its (nonzero) digits is 12960, while the sum is 37.

The square root of 129821905 is about 11393.9415919163. The cubic root of 129821905 is about 506.3482646219.

The spelling of 129821905 in words is "one hundred twenty-nine million, eight hundred twenty-one thousand, nine hundred five".