721613 has 2 divisors, whose sum is σ = 721614. Its totient is φ = 721612.

The previous prime is 721597. The next prime is 721619. The reversal of 721613 is 316127.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 405769 + 315844 = 637^2 + 562^2 .

721613 is a truncatable prime.

It is a cyclic number.

It is not a de Polignac number, because 721613 - 2⁴ = 721597 is a prime.

It is a Chen prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721613.

It is not a weakly prime, because it can be changed into another prime (721619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360806 + 360807.

It is an arithmetic number, because the mean of its divisors is an integer number (360807).

2⁷²¹⁶¹³ is an apocalyptic number.

It is an amenable number.

721613 is a deficient number, since it is larger than the sum of its proper divisors (1).

721613 is an equidigital number, since it uses as much as digits as its factorization.

721613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 252, while the sum is 20.

The square root of 721613 is about 849.4780750555. The cubic root of 721613 is about 89.6949756220.

The spelling of 721613 in words is "seven hundred twenty-one thousand, six hundred thirteen".