655721 has 4 divisors (see below), whose sum is σ = 715344. Its totient is φ = 596100.

The previous prime is 655717. The next prime is 655723. The reversal of 655721 is 127556.

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 655721 - 2² = 655717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (655723) 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, 29795 + ... + 29816.

It is an arithmetic number, because the mean of its divisors is an integer number (178836).

2⁶⁵⁵⁷²¹ is an apocalyptic number.

It is an amenable number.

655721 is a deficient number, since it is larger than the sum of its proper divisors (59623).

655721 is a wasteful number, since it uses less digits than its factorization.

655721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59622.

The product of its digits is 2100, while the sum is 26.

The square root of 655721 is about 809.7660155872. The cubic root of 655721 is about 86.8773097742.

The spelling of 655721 in words is "six hundred fifty-five thousand, seven hundred twenty-one".