121355561 has 4 divisors (see below), whose sum is σ = 121461072. Its totient is φ = 121250052.

The previous prime is 121355513. The next prime is 121355579. The reversal of 121355561 is 165553121.

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, and also an emirpimes, since its reverse is a distinct semiprime: 165553121 = 41 ⋅4037881.

It is a cyclic number.

It is not a de Polignac number, because 121355561 - 2¹⁰ = 121354537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121355501) 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 3 ways as a sum of consecutive naturals, for example, 51011 + ... + 53336.

It is an arithmetic number, because the mean of its divisors is an integer number (30365268).

Almost surely, 2^121355561 is an apocalyptic number.

It is an amenable number.

121355561 is a deficient number, since it is larger than the sum of its proper divisors (105511).

121355561 is a wasteful number, since it uses less digits than its factorization.

121355561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105510.

The product of its digits is 4500, while the sum is 29.

The square root of 121355561 is about 11016.1500080564. The cubic root of 121355561 is about 495.0927432252.

The spelling of 121355561 in words is "one hundred twenty-one million, three hundred fifty-five thousand, five hundred sixty-one".