77721 has 8 divisors (see below), whose sum is σ = 118464. Its totient is φ = 44400.

The previous prime is 77719. The next prime is 77723. The reversal of 77721 is 12777.

It is an interprime number because it is at equal distance from previous prime (77719) and next prime (77723).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 77721 - 2¹ = 77719 is a prime.

It is a Curzon number.

77721 is a lucky number.

It is a nialpdrome in base 10.

It is a junction number, because it is equal to n+sod(n) for n = 77691 and 77700.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 77721.

It is not an unprimeable number, because it can be changed into a prime (77723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1830 + ... + 1871.

It is an arithmetic number, because the mean of its divisors is an integer number (14808).

2⁷⁷⁷²¹ is an apocalyptic number.

It is an amenable number.

77721 is a deficient number, since it is larger than the sum of its proper divisors (40743).

77721 is a wasteful number, since it uses less digits than its factorization.

77721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3711.

The product of its digits is 686, while the sum is 24.

The square root of 77721 is about 278.7848632907. The cubic root of 77721 is about 42.6755827178.

The spelling of 77721 in words is "seventy-seven thousand, seven hundred twenty-one", and thus it is an iban number.