721693 has 4 divisors (see below), whose sum is σ = 824800. Its totient is φ = 618588.

The previous prime is 721687. The next prime is 721697. The reversal of 721693 is 396127.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 396127 = 179 ⋅2213.

It is a cyclic number.

It is not a de Polignac number, because 721693 - 2⁵ = 721661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721697) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 51543 + ... + 51556.

It is an arithmetic number, because the mean of its divisors is an integer number (206200).

2⁷²¹⁶⁹³ is an apocalyptic number.

It is an amenable number.

721693 is a deficient number, since it is larger than the sum of its proper divisors (103107).

721693 is a wasteful number, since it uses less digits than its factorization.

721693 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103106.

The product of its digits is 2268, while the sum is 28.

The square root of 721693 is about 849.5251614873. The cubic root of 721693 is about 89.6982901100.

The spelling of 721693 in words is "seven hundred twenty-one thousand, six hundred ninety-three".