766071721 has 6 divisors (see below), whose sum is σ = 791581866. Its totient is φ = 741358800.

The previous prime is 766071701. The next prime is 766071749. The reversal of 766071721 is 127170667.

It can be written as a sum of positive squares in only one way, i.e., 549246096 + 216825625 = 23436^2 + 14725^2 .

It is not a de Polignac number, because 766071721 - 2⁹ = 766071209 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (766071701) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 397620 + ... + 399541.

It is an arithmetic number, because the mean of its divisors is an integer number (131930311).

Almost surely, 2^766071721 is an apocalyptic number.

It is an amenable number.

766071721 is a deficient number, since it is larger than the sum of its proper divisors (25510145).

766071721 is an equidigital number, since it uses as much as digits as its factorization.

766071721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 797223 (or 797192 counting only the distinct ones).

The product of its (nonzero) digits is 24696, while the sum is 37.

The square root of 766071721 is about 27678.0006684009. Note that the first 3 decimals coincide. The cubic root of 766071721 is about 915.0043182135.

Subtracting from 766071721 its sum of digits (37), we obtain a square (766071684 = 27678²).

The spelling of 766071721 in words is "seven hundred sixty-six million, seventy-one thousand, seven hundred twenty-one".