123201821 has 2 divisors, whose sum is σ = 123201822. Its totient is φ = 123201820.

The previous prime is 123201817. The next prime is 123201829. The reversal of 123201821 is 128102321.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 120012025 + 3189796 = 10955^2 + 1786^2 .

It is an emirp because it is prime and its reverse (128102321) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 123201821 - 2² = 123201817 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 123201793 and 123201802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (123201829) 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 as a sum of consecutive naturals, namely, 61600910 + 61600911.

It is an arithmetic number, because the mean of its divisors is an integer number (61600911).

Almost surely, 2^123201821 is an apocalyptic number.

It is an amenable number.

123201821 is a deficient number, since it is larger than the sum of its proper divisors (1).

123201821 is an equidigital number, since it uses as much as digits as its factorization.

123201821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 123201821 is about 11099.6315704621. The cubic root of 123201821 is about 497.5908385259.

It can be divided in two parts, 12320 and 1821, that added together give a palindrome (14141).

The spelling of 123201821 in words is "one hundred twenty-three million, two hundred one thousand, eight hundred twenty-one".