721553 has 4 divisors (see below), whose sum is σ = 824640. Its totient is φ = 618468.

The previous prime is 721547. The next prime is 721561. The reversal of 721553 is 355127.

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.

It is a cyclic number.

It is not a de Polignac number, because 721553 - 2¹⁴ = 705169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (723553) 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, 51533 + ... + 51546.

It is an arithmetic number, because the mean of its divisors is an integer number (206160).

2⁷²¹⁵⁵³ is an apocalyptic number.

It is an amenable number.

721553 is a deficient number, since it is larger than the sum of its proper divisors (103087).

721553 is a wasteful number, since it uses less digits than its factorization.

721553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 103086.

The product of its digits is 1050, while the sum is 23.

The square root of 721553 is about 849.4427585188. The cubic root of 721553 is about 89.6924895952.

The spelling of 721553 in words is "seven hundred twenty-one thousand, five hundred fifty-three".