79721 has 4 divisors (see below), whose sum is σ = 82500. Its totient is φ = 76944.

The previous prime is 79699. The next prime is 79757. The reversal of 79721 is 12797.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12797 = 67 ⋅191.

It can be written as a sum of positive squares in 2 ways, for example, as 24025 + 55696 = 155^2 + 236^2 .

It is a cyclic number.

It is not a de Polignac number, because 79721 - 2⁶ = 79657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (79621) 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, 1346 + ... + 1403.

It is an arithmetic number, because the mean of its divisors is an integer number (20625).

2⁷⁹⁷²¹ is an apocalyptic number.

It is an amenable number.

79721 is a deficient number, since it is larger than the sum of its proper divisors (2779).

79721 is a wasteful number, since it uses less digits than its factorization.

79721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2778.

The product of its digits is 882, while the sum is 26.

The square root of 79721 is about 282.3490747284. The cubic root of 79721 is about 43.0385448507.

It can be divided in two parts, 797 and 21, that added together give a palindrome (818).

The spelling of 79721 in words is "seventy-nine thousand, seven hundred twenty-one".