129656521 has 2 divisors, whose sum is σ = 129656522. Its totient is φ = 129656520.

The previous prime is 129656519. The next prime is 129656561. The reversal of 129656521 is 125656921.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 123210000 + 6446521 = 11100^2 + 2539^2 .

It is a cyclic number.

It is not a de Polignac number, because 129656521 - 2¹ = 129656519 is a prime.

Together with 129656519, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between odd and even.

It is not a weakly prime, because it can be changed into another prime (129656561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64828260 + 64828261.

It is an arithmetic number, because the mean of its divisors is an integer number (64828261).

Almost surely, 2^129656521 is an apocalyptic number.

It is an amenable number.

129656521 is a deficient number, since it is larger than the sum of its proper divisors (1).

129656521 is an equidigital number, since it uses as much as digits as its factorization.

129656521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32400, while the sum is 37.

The square root of 129656521 is about 11386.6817378901. The cubic root of 129656521 is about 506.1331558619.

The spelling of 129656521 in words is "one hundred twenty-nine million, six hundred fifty-six thousand, five hundred twenty-one".