67721 has 4 divisors (see below), whose sum is σ = 68244. Its totient is φ = 67200.

The previous prime is 67709. The next prime is 67723. The reversal of 67721 is 12776.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 48400 + 19321 = 220^2 + 139^2 .

It is a cyclic number.

It is not a de Polignac number, because 67721 - 2¹⁰ = 66697 is a prime.

It is a super-2 number, since 2×67721² = 9172267682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (67723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 101 + ... + 381.

It is an arithmetic number, because the mean of its divisors is an integer number (17061).

2⁶⁷⁷²¹ is an apocalyptic number.

It is an amenable number.

67721 is a deficient number, since it is larger than the sum of its proper divisors (523).

67721 is a wasteful number, since it uses less digits than its factorization.

67721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 522.

The product of its digits is 588, while the sum is 23.

The square root of 67721 is about 260.2325882744. The cubic root of 67721 is about 40.7606518631.

Subtracting from 67721 its reverse (12776), we obtain a palindrome (54945).

The spelling of 67721 in words is "sixty-seven thousand, seven hundred twenty-one".