121556161 has 4 divisors (see below), whose sum is σ = 122227924. Its totient is φ = 120884400.

The previous prime is 121556153. The next prime is 121556179. The reversal of 121556161 is 161655121.

121556161 = T₃₇₉ + T₃₈₀ + ... + T₉₂₁.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 161655121 = 67 ⋅2412763.

It can be written as a sum of positive squares in 2 ways, for example, as 18147600 + 103408561 = 4260^2 + 10169^2 .

It is a cyclic number.

It is not a de Polignac number, because 121556161 - 2³ = 121556153 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121556101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 335610 + ... + 335971.

It is an arithmetic number, because the mean of its divisors is an integer number (30556981).

Almost surely, 2^121556161 is an apocalyptic number.

It is an amenable number.

121556161 is a deficient number, since it is larger than the sum of its proper divisors (671763).

121556161 is an equidigital number, since it uses as much as digits as its factorization.

121556161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 671762.

The product of its digits is 1800, while the sum is 28.

The square root of 121556161 is about 11025.2510629010. The cubic root of 121556161 is about 495.3653881456.

The spelling of 121556161 in words is "one hundred twenty-one million, five hundred fifty-six thousand, one hundred sixty-one".