76721 has 4 divisors (see below), whose sum is σ = 81252. Its totient is φ = 72192.

The previous prime is 76717. The next prime is 76733. The reversal of 76721 is 12767.

76721 = 59² + 60² + ... + 75².

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12767 = 17 ⋅751.

It can be written as a sum of positive squares in 2 ways, for example, as 21025 + 55696 = 145^2 + 236^2 .

It is a cyclic number.

It is not a de Polignac number, because 76721 - 2² = 76717 is a prime.

It is a super-2 number, since 2×76721² = 11772223682, which contains 22 as substring.

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

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (76771) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2240 + ... + 2273.

It is an arithmetic number, because the mean of its divisors is an integer number (20313).

2⁷⁶⁷²¹ is an apocalyptic number.

It is an amenable number.

76721 is a deficient number, since it is larger than the sum of its proper divisors (4531).

76721 is a wasteful number, since it uses less digits than its factorization.

76721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4530.

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

The square root of 76721 is about 276.9855591904. The cubic root of 76721 is about 42.4917631096.

It can be divided in two parts, 76 and 721, that added together give a palindrome (797).

The spelling of 76721 in words is "seventy-six thousand, seven hundred twenty-one".