7721 has 4 divisors (see below), whose sum is σ = 8832.
Its totient is φ = 6612.
The previous prime is 7717. The next prime is 7723. The reversal of 7721 is 1277.
It is a happy number.
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 7721 - 22 = 7717 is a prime.
It is a super-2 number, since 2×77212 = 119227682, which contains 22 as substring.
It is a Duffinian number.
It is a Curzon number.
It is a plaindrome in base 11, base 13 and base 15.
It is a nialpdrome in base 10.
It is a self number, because there is not a number n which added to its sum of digits gives 7721.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (7723) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 545 + ... + 558.
It is an arithmetic number, because the mean of its divisors is an integer number (2208).
It is an amenable number.
7721 is a deficient number, since it is larger than the sum of its proper divisors (1111).
7721 is a wasteful number, since it uses less digits than its factorization.
7721 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1110.
The product of its digits is 98, while the sum is 17.
The square root of 7721 is about 87.8692210049.
The cubic root of 7721 is about 19.7647435710.
Adding to 7721 its reverse (1277), we get a palindrome (8998).
The spelling of 7721 in words is "seven thousand, seven hundred twenty-one", and thus it is an iban number.