720256721 has 2 divisors, whose sum is σ = 720256722. Its totient is φ = 720256720.

The previous prime is 720256711. The next prime is 720256723. The reversal of 720256721 is 127652027.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 582546496 + 137710225 = 24136^2 + 11735^2 .

It is an emirp because it is prime and its reverse (127652027) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 720256721 - 2¹⁴ = 720240337 is a prime.

Together with 720256723, 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 (720256723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360128360 + 360128361.

It is an arithmetic number, because the mean of its divisors is an integer number (360128361).

Almost surely, 2^720256721 is an apocalyptic number.

It is an amenable number.

720256721 is a deficient number, since it is larger than the sum of its proper divisors (1).

720256721 is an equidigital number, since it uses as much as digits as its factorization.

720256721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11760, while the sum is 32.

The square root of 720256721 is about 26837.5990170507. The cubic root of 720256721 is about 896.3874617187.

The spelling of 720256721 in words is "seven hundred twenty million, two hundred fifty-six thousand, seven hundred twenty-one".