647221 has 4 divisors (see below), whose sum is σ = 649792. Its totient is φ = 644652.

The previous prime is 647219. The next prime is 647261. The reversal of 647221 is 122746.

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 647221 - 2¹ = 647219 is a prime.

It is the 805-th Hogben number.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 647192 and 647201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (647201) by changing a digit.

It is a nontrivial repunit in base 804.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 861 + ... + 1426.

It is an arithmetic number, because the mean of its divisors is an integer number (162448).

2⁶⁴⁷²²¹ is an apocalyptic number.

It is an amenable number.

647221 is a deficient number, since it is larger than the sum of its proper divisors (2571).

647221 is a wasteful number, since it uses less digits than its factorization.

647221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2570.

The product of its digits is 672, while the sum is 22.

The square root of 647221 is about 804.5004661279. The cubic root of 647221 is about 86.5002840045.

Adding to 647221 its reverse (122746), we get a palindrome (769967).

It can be divided in two parts, 647 and 221, that added together give a palindrome (868).

The spelling of 647221 in words is "six hundred forty-seven thousand, two hundred twenty-one".