123210721 has 4 divisors (see below), whose sum is σ = 123505200. Its totient is φ = 122916244.

The previous prime is 123210719. The next prime is 123210739. The reversal of 123210721 is 127012321.

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.

It is a cyclic number.

It is not a de Polignac number, because 123210721 - 2¹ = 123210719 is a prime.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (123210751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 146611 + ... + 147448.

It is an arithmetic number, because the mean of its divisors is an integer number (30876300).

Almost surely, 2^123210721 is an apocalyptic number.

It is an amenable number.

123210721 is a deficient number, since it is larger than the sum of its proper divisors (294479).

123210721 is an equidigital number, since it uses as much as digits as its factorization.

123210721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294478.

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 123210721 is about 11100.0324774300. The cubic root of 123210721 is about 497.6028200907.

The spelling of 123210721 in words is "one hundred twenty-three million, two hundred ten thousand, seven hundred twenty-one".