123721 has 8 divisors (see below), whose sum is σ = 137984. Its totient is φ = 110160.

The previous prime is 123719. The next prime is 123727. The reversal of 123721 is 127321.

It is a happy number.

123721 is nontrivially palindromic in base 14.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 123721 - 2¹ = 123719 is a prime.

It is a Duffinian number.

123721 is a lucky number.

It is a nialpdrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 123695 and 123704.

It is not an unprimeable number, because it can be changed into a prime (123727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 250 + ... + 556.

It is an arithmetic number, because the mean of its divisors is an integer number (17248).

2¹²³⁷²¹ is an apocalyptic number.

It is an amenable number.

123721 is a deficient number, since it is larger than the sum of its proper divisors (14263).

123721 is a wasteful number, since it uses less digits than its factorization.

123721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351.

The product of its digits is 84, while the sum is 16.

The square root of 123721 is about 351.7399607665. The cubic root of 123721 is about 49.8288817053.

Subtracting 123721 from its reverse (127321), we obtain a square (3600 = 60²).

The spelling of 123721 in words is "one hundred twenty-three thousand, seven hundred twenty-one", and thus it is an iban number.