721697 has 2 divisors, whose sum is σ = 721698. Its totient is φ = 721696.

The previous prime is 721687. The next prime is 721703. The reversal of 721697 is 796127.

Added to its reverse (796127) it gives a square (1517824 = 1232²).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 698896 + 22801 = 836^2 + 151^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721697 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (721687) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360848 + 360849.

It is an arithmetic number, because the mean of its divisors is an integer number (360849).

2⁷²¹⁶⁹⁷ is an apocalyptic number.

It is an amenable number.

721697 is a deficient number, since it is larger than the sum of its proper divisors (1).

721697 is an equidigital number, since it uses as much as digits as its factorization.

721697 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5292, while the sum is 32.

The square root of 721697 is about 849.5275157404. The cubic root of 721697 is about 89.6984558280.

Adding to 721697 its reverse (796127), we get a square (1517824 = 1232²).

The spelling of 721697 in words is "seven hundred twenty-one thousand, six hundred ninety-seven".