18991129 has 2 divisors, whose sum is σ = 18991130. Its totient is φ = 18991128.

The previous prime is 18991121. The next prime is 18991139. The reversal of 18991129 is 92119981.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17867529 + 1123600 = 4227^2 + 1060^2 .

It is a cyclic number.

It is not a de Polignac number, because 18991129 - 2³ = 18991121 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 18991091 and 18991100.

It is not a weakly prime, because it can be changed into another prime (18991121) by changing a digit.

It is an upside-down number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9495564 + 9495565.

It is an arithmetic number, because the mean of its divisors is an integer number (9495565).

Almost surely, 2^18991129 is an apocalyptic number.

It is an amenable number.

18991129 is a deficient number, since it is larger than the sum of its proper divisors (1).

18991129 is an equidigital number, since it uses as much as digits as its factorization.

18991129 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11664, while the sum is 40.

The square root of 18991129 is about 4357.8812512504. The cubic root of 18991129 is about 266.7986296511.

The spelling of 18991129 in words is "eighteen million, nine hundred ninety-one thousand, one hundred twenty-nine".