121556681 has 4 divisors (see below), whose sum is σ = 128707092. Its totient is φ = 114406272.

The previous prime is 121556671. The next prime is 121556689. The reversal of 121556681 is 186655121.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 97693456 + 23863225 = 9884^2 + 4885^2 .

It is a cyclic number.

It is not a de Polignac number, because 121556681 - 2²⁶ = 54447817 is a prime.

It is a super-2 number, since 2×121556681² = 29552053391471522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (121556689) 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, 3575180 + ... + 3575213.

It is an arithmetic number, because the mean of its divisors is an integer number (32176773).

Almost surely, 2^121556681 is an apocalyptic number.

It is an amenable number.

121556681 is a deficient number, since it is larger than the sum of its proper divisors (7150411).

121556681 is an equidigital number, since it uses as much as digits as its factorization.

121556681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7150410.

The product of its digits is 14400, while the sum is 35.

The square root of 121556681 is about 11025.2746451052. The cubic root of 121556681 is about 495.3660945122.

The spelling of 121556681 in words is "one hundred twenty-one million, five hundred fifty-six thousand, six hundred eighty-one".