645491 has 16 divisors (see below), whose sum is σ = 822528. Its totient is φ = 492000.

The previous prime is 645481. The next prime is 645493. The reversal of 645491 is 194546.

It is a cyclic number.

It is not a de Polignac number, because 645491 - 2¹⁸ = 383347 is a prime.

It is not an unprimeable number, because it can be changed into a prime (645493) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6341 + ... + 6441.

It is an arithmetic number, because the mean of its divisors is an integer number (51408).

2⁶⁴⁵⁴⁹¹ is an apocalyptic number.

645491 is a deficient number, since it is larger than the sum of its proper divisors (177037).

645491 is a wasteful number, since it uses less digits than its factorization.

645491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 202.

The product of its digits is 4320, while the sum is 29.

The square root of 645491 is about 803.4245453059. The cubic root of 645491 is about 86.4231444483.

It can be divided in two parts, 64 and 5491, that added together give a palindrome (5555).

The spelling of 645491 in words is "six hundred forty-five thousand, four hundred ninety-one".