121256821 has 6 divisors (see below), whose sum is σ = 141053910. Its totient is φ = 103934376.

The previous prime is 121256819. The next prime is 121256867. The reversal of 121256821 is 128652121.

It can be written as a sum of positive squares in only one way, i.e., 103734225 + 17522596 = 10185^2 + 4186^2 .

It is not a de Polignac number, because 121256821 - 2¹ = 121256819 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 121256821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121256321) 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 5 ways as a sum of consecutive naturals, for example, 1237266 + ... + 1237363.

It is an arithmetic number, because the mean of its divisors is an integer number (23508985).

Almost surely, 2^121256821 is an apocalyptic number.

It is an amenable number.

121256821 is a deficient number, since it is larger than the sum of its proper divisors (19797089).

121256821 is an equidigital number, since it uses as much as digits as its factorization.

121256821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2474643 (or 2474636 counting only the distinct ones).

The product of its digits is 1920, while the sum is 28.

The square root of 121256821 is about 11011.6674940719. The cubic root of 121256821 is about 494.9584306826.

The spelling of 121256821 in words is "one hundred twenty-one million, two hundred fifty-six thousand, eight hundred twenty-one".