721397 has 2 divisors, whose sum is σ = 721398. Its totient is φ = 721396.

The previous prime is 721387. The next prime is 721439. The reversal of 721397 is 793127.

It is a happy number.

721397 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 568516 + 152881 = 754^2 + 391^2 .

It is a cyclic number.

It is not a de Polignac number, because 721397 - 2⁴ = 721381 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (721307) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360698 + 360699.

It is an arithmetic number, because the mean of its divisors is an integer number (360699).

2⁷²¹³⁹⁷ is an apocalyptic number.

It is an amenable number.

721397 is a deficient number, since it is larger than the sum of its proper divisors (1).

721397 is an equidigital number, since it uses as much as digits as its factorization.

721397 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2646, while the sum is 29.

The square root of 721397 is about 849.3509286508. The cubic root of 721397 is about 89.6860252806.

The spelling of 721397 in words is "seven hundred twenty-one thousand, three hundred ninety-seven".