643621 has 4 divisors (see below), whose sum is σ = 702144. Its totient is φ = 585100.

The previous prime is 643619. The next prime is 643633. The reversal of 643621 is 126346.

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 643621 - 2¹ = 643619 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam 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 = 643592 and 643601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643651) 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, 29245 + ... + 29266.

It is an arithmetic number, because the mean of its divisors is an integer number (175536).

2⁶⁴³⁶²¹ is an apocalyptic number.

It is an amenable number.

643621 is a deficient number, since it is larger than the sum of its proper divisors (58523).

643621 is a wasteful number, since it uses less digits than its factorization.

643621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58522.

The product of its digits is 864, while the sum is 22.

The square root of 643621 is about 802.2599329394. The cubic root of 643621 is about 86.3396072157.

Adding to 643621 its reverse (126346), we get a palindrome (769967).

It can be divided in two parts, 6 and 43621, that multiplied together give a triangular number (261726 = T₇₂₃).

The spelling of 643621 in words is "six hundred forty-three thousand, six hundred twenty-one".