121553565881 has 16 divisors (see below), whose sum is σ = 145651875840. Its totient is φ = 100135656720.

The previous prime is 121553565799. The next prime is 121553565899. The reversal of 121553565881 is 188565355121.

It is a happy number.

It is not a de Polignac number, because 121553565881 - 2¹⁴ = 121553549497 is a prime.

It is a super-2 number, since 2×121553565881² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (121550565881) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12638585 + ... + 12648198.

It is an arithmetic number, because the mean of its divisors is an integer number (9103242240).

Almost surely, 2^121553565881 is an apocalyptic number.

121553565881 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

121553565881 is a deficient number, since it is larger than the sum of its proper divisors (24098309959).

121553565881 is a wasteful number, since it uses less digits than its factorization.

121553565881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25286836.

The product of its digits is 1440000, while the sum is 50.

The spelling of 121553565881 in words is "one hundred twenty-one billion, five hundred fifty-three million, five hundred sixty-five thousand, eight hundred eighty-one".