129191021 has 4 divisors (see below), whose sum is σ = 130177344. Its totient is φ = 128204700.

The previous prime is 129191011. The next prime is 129191053. The reversal of 129191021 is 120191921.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-129191021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (129191011) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 492965 + ... + 493226.

It is an arithmetic number, because the mean of its divisors is an integer number (32544336).

Almost surely, 2^129191021 is an apocalyptic number.

It is an amenable number.

129191021 is a deficient number, since it is larger than the sum of its proper divisors (986323).

129191021 is an equidigital number, since it uses as much as digits as its factorization.

129191021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 986322.

The product of its (nonzero) digits is 324, while the sum is 26.

The square root of 129191021 is about 11366.2228114708. Note that the first 3 decimals coincide. The cubic root of 129191021 is about 505.5267137880.

The spelling of 129191021 in words is "one hundred twenty-nine million, one hundred ninety-one thousand, twenty-one".