766216721 has 2 divisors, whose sum is σ = 766216722. Its totient is φ = 766216720.

The previous prime is 766216709. The next prime is 766216723. The reversal of 766216721 is 127612667.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 431143696 + 335073025 = 20764^2 + 18305^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-766216721 is a prime.

It is a super-3 number, since 3×766216721³ (a number of 28 digits) contains 333 as substring.

Together with 766216723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (766216723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 383108360 + 383108361.

It is an arithmetic number, because the mean of its divisors is an integer number (383108361).

Almost surely, 2^766216721 is an apocalyptic number.

It is an amenable number.

766216721 is a deficient number, since it is larger than the sum of its proper divisors (1).

766216721 is an equidigital number, since it uses as much as digits as its factorization.

766216721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 42336, while the sum is 38.

The square root of 766216721 is about 27680.6199533175. The cubic root of 766216721 is about 915.0620444257.

The spelling of 766216721 in words is "seven hundred sixty-six million, two hundred sixteen thousand, seven hundred twenty-one".