55721 has 2 divisors, whose sum is σ = 55722. Its totient is φ = 55720.

The previous prime is 55717. The next prime is 55733. The reversal of 55721 is 12755.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 55696 + 25 = 236^2 + 5^2 .

It is a cyclic number.

It is not a de Polignac number, because 55721 - 2² = 55717 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a plaindrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 55693 and 55702.

It is not a weakly prime, because it can be changed into another prime (55711) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 27860 + 27861.

It is an arithmetic number, because the mean of its divisors is an integer number (27861).

2⁵⁵⁷²¹ is an apocalyptic number.

It is an amenable number.

55721 is a deficient number, since it is larger than the sum of its proper divisors (1).

55721 is an equidigital number, since it uses as much as digits as its factorization.

55721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 350, while the sum is 20.

The square root of 55721 is about 236.0529601594. The cubic root of 55721 is about 38.1949812034.

The spelling of 55721 in words is "fifty-five thousand, seven hundred twenty-one".