999809709121 has 2 divisors, whose sum is σ = 999809709122. Its totient is φ = 999809709120.

The previous prime is 999809709113. The next prime is 999809709163. The reversal of 999809709121 is 121907908999.

999809709121 = 707039² + 707040².

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 499905561600 + 499904147521 = 707040^2 + 707039^2 .

It is a cyclic number.

It is not a de Polignac number, because 999809709121 - 2³ = 999809709113 is a prime.

It is not a weakly prime, because it can be changed into another prime (999809709181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499904854560 + 499904854561.

It is an arithmetic number, because the mean of its divisors is an integer number (499904854561).

Almost surely, 2^999809709121 is an apocalyptic number.

999809709121 is the 707040-th centered square number.

It is an amenable number.

999809709121 is a deficient number, since it is larger than the sum of its proper divisors (1).

999809709121 is an equidigital number, since it uses as much as digits as its factorization.

999809709121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6613488, while the sum is 64.

The spelling of 999809709121 in words is "nine hundred ninety-nine billion, eight hundred nine million, seven hundred nine thousand, one hundred twenty-one".