121815909 has 6 divisors (see below), whose sum is σ = 175956326. Its totient is φ = 81210600.

The previous prime is 121815899. The next prime is 121815949. The reversal of 121815909 is 909518121.

It can be written as a sum of positive squares in only one way, i.e., 76212900 + 45603009 = 8730^2 + 6753^2 .

It is not a de Polignac number, because 121815909 - 2¹⁶ = 121750373 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 (121815949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6767542 + ... + 6767559.

Almost surely, 2^121815909 is an apocalyptic number.

It is an amenable number.

121815909 is a deficient number, since it is larger than the sum of its proper divisors (54140417).

121815909 is a wasteful number, since it uses less digits than its factorization.

121815909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13535107 (or 13535104 counting only the distinct ones).

The product of its (nonzero) digits is 6480, while the sum is 36.

The square root of 121815909 is about 11037.0244631422. The cubic root of 121815909 is about 495.7179786041.

The spelling of 121815909 in words is "one hundred twenty-one million, eight hundred fifteen thousand, nine hundred nine".