778721 has 4 divisors (see below), whose sum is σ = 783552. Its totient is φ = 773892.

The previous prime is 778717. The next prime is 778727. The reversal of 778721 is 127877.

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 778721 - 2² = 778717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (778727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2165 + ... + 2498.

It is an arithmetic number, because the mean of its divisors is an integer number (195888).

2⁷⁷⁸⁷²¹ is an apocalyptic number.

It is an amenable number.

778721 is a deficient number, since it is larger than the sum of its proper divisors (4831).

778721 is a wasteful number, since it uses less digits than its factorization.

778721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4830.

The product of its digits is 5488, while the sum is 32.

The square root of 778721 is about 882.4516983949. The cubic root of 778721 is about 92.0012996036.

The spelling of 778721 in words is "seven hundred seventy-eight thousand, seven hundred twenty-one".