129565021 has 2 divisors, whose sum is σ = 129565022. Its totient is φ = 129565020.

The previous prime is 129565013. The next prime is 129565057. The reversal of 129565021 is 120565921.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 96628900 + 32936121 = 9830^2 + 5739^2 .

It is a cyclic number.

It is not a de Polignac number, because 129565021 - 2³ = 129565013 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (129565061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64782510 + 64782511.

It is an arithmetic number, because the mean of its divisors is an integer number (64782511).

Almost surely, 2^129565021 is an apocalyptic number.

It is an amenable number.

129565021 is a deficient number, since it is larger than the sum of its proper divisors (1).

129565021 is an equidigital number, since it uses as much as digits as its factorization.

129565021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5400, while the sum is 31.

The square root of 129565021 is about 11382.6631769547. The cubic root of 129565021 is about 506.0140666412.

The spelling of 129565021 in words is "one hundred twenty-nine million, five hundred sixty-five thousand, twenty-one".