721993 has 4 divisors (see below), whose sum is σ = 753408. Its totient is φ = 690580.

The previous prime is 721991. The next prime is 721997. The reversal of 721993 is 399127.

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: 399127 = 29 ⋅13763.

It is a cyclic number.

It is not a de Polignac number, because 721993 - 2¹ = 721991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721991) 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 in 3 ways as a sum of consecutive naturals, for example, 15673 + ... + 15718.

It is an arithmetic number, because the mean of its divisors is an integer number (188352).

2⁷²¹⁹⁹³ is an apocalyptic number.

It is an amenable number.

721993 is a deficient number, since it is larger than the sum of its proper divisors (31415).

721993 is a wasteful number, since it uses less digits than its factorization.

721993 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31414.

The product of its digits is 3402, while the sum is 31.

The square root of 721993 is about 849.7017123673. The cubic root of 721993 is about 89.7107172589.

The spelling of 721993 in words is "seven hundred twenty-one thousand, nine hundred ninety-three".