721728257 has 2 divisors, whose sum is σ = 721728258. Its totient is φ = 721728256.

The previous prime is 721728223. The next prime is 721728283. The reversal of 721728257 is 752827127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 377291776 + 344436481 = 19424^2 + 18559^2 .

It is a cyclic number.

It is not a de Polignac number, because 721728257 - 2²² = 717533953 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (721728157) 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 as a sum of consecutive naturals, namely, 360864128 + 360864129.

It is an arithmetic number, because the mean of its divisors is an integer number (360864129).

Almost surely, 2^721728257 is an apocalyptic number.

It is an amenable number.

721728257 is a deficient number, since it is larger than the sum of its proper divisors (1).

721728257 is an equidigital number, since it uses as much as digits as its factorization.

721728257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 109760, while the sum is 41.

The square root of 721728257 is about 26865.0005955704. Note that the first 3 decimals coincide. The cubic root of 721728257 is about 896.9975076852.

The spelling of 721728257 in words is "seven hundred twenty-one million, seven hundred twenty-eight thousand, two hundred fifty-seven".