129721811 has 2 divisors, whose sum is σ = 129721812. Its totient is φ = 129721810.

The previous prime is 129721783. The next prime is 129721819. The reversal of 129721811 is 118127921.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-129721811 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (129721819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64860905 + 64860906.

It is an arithmetic number, because the mean of its divisors is an integer number (64860906).

Almost surely, 2^129721811 is an apocalyptic number.

129721811 is a deficient number, since it is larger than the sum of its proper divisors (1).

129721811 is an equidigital number, since it uses as much as digits as its factorization.

129721811 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2016, while the sum is 32.

The square root of 129721811 is about 11389.5483229143. The cubic root of 129721811 is about 506.2180979541.

The spelling of 129721811 in words is "one hundred twenty-nine million, seven hundred twenty-one thousand, eight hundred eleven".