645621 has 8 divisors (see below), whose sum is σ = 864864. Its totient is φ = 428400.

The previous prime is 645611. The next prime is 645629. The reversal of 645621 is 126546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 645621 - 2⁷ = 645493 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 645591 and 645600.

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 645621.

It is not an unprimeable number, because it can be changed into a prime (645629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 571 + ... + 1271.

It is an arithmetic number, because the mean of its divisors is an integer number (108108).

2⁶⁴⁵⁶²¹ is an apocalyptic number.

It is an amenable number.

645621 is a deficient number, since it is larger than the sum of its proper divisors (219243).

645621 is a wasteful number, since it uses less digits than its factorization.

645621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1011.

The product of its digits is 1440, while the sum is 24.

The square root of 645621 is about 803.5054449100. The cubic root of 645621 is about 86.4289458484.

The spelling of 645621 in words is "six hundred forty-five thousand, six hundred twenty-one".