721653 has 4 divisors (see below), whose sum is σ = 962208. Its totient is φ = 481100.

The previous prime is 721631. The next prime is 721661. The reversal of 721653 is 356127.

721653 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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: 356127 = 3 ⋅118709.

It is a cyclic number.

It is not a de Polignac number, because 721653 - 2⁵ = 721621 is a prime.

It is a D-number.

It is a Curzon number.

721653 is a lucky number.

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 721653.

It is not an unprimeable number, because it can be changed into a prime (721613) 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, 120273 + ... + 120278.

It is an arithmetic number, because the mean of its divisors is an integer number (240552).

2⁷²¹⁶⁵³ is an apocalyptic number.

It is an amenable number.

721653 is a deficient number, since it is larger than the sum of its proper divisors (240555).

721653 is a wasteful number, since it uses less digits than its factorization.

721653 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 240554.

The product of its digits is 1260, while the sum is 24.

The square root of 721653 is about 849.5016185976. The cubic root of 721653 is about 89.6966328966.

The spelling of 721653 in words is "seven hundred twenty-one thousand, six hundred fifty-three".