766555721 has 8 divisors (see below), whose sum is σ = 831444264. Its totient is φ = 703866880.

The previous prime is 766555709. The next prime is 766555729. The reversal of 766555721 is 127555667.

766555721 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 373321 + 766182400 = 611^2 + 27680^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 766555721 - 2¹⁰ = 766554697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (766555729) 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, 549200 + ... + 550593.

It is an arithmetic number, because the mean of its divisors is an integer number (103930533).

Almost surely, 2^766555721 is an apocalyptic number.

It is an amenable number.

766555721 is a deficient number, since it is larger than the sum of its proper divisors (64888543).

766555721 is a wasteful number, since it uses less digits than its factorization.

766555721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1099851.

The product of its digits is 441000, while the sum is 44.

The square root of 766555721 is about 27686.7426939321. The cubic root of 766555721 is about 915.1969759175.

The spelling of 766555721 in words is "seven hundred sixty-six million, five hundred fifty-five thousand, seven hundred twenty-one".