646491 has 4 divisors (see below), whose sum is σ = 861992. Its totient is φ = 430992.

The previous prime is 646453. The next prime is 646519. The reversal of 646491 is 194646.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 646491 - 2⁹ = 645979 is a prime.

It is a super-2 number, since 2×646491² = 835901226162, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646411) 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 3 ways as a sum of consecutive naturals, for example, 107746 + ... + 107751.

It is an arithmetic number, because the mean of its divisors is an integer number (215498).

2⁶⁴⁶⁴⁹¹ is an apocalyptic number.

646491 is a deficient number, since it is larger than the sum of its proper divisors (215501).

646491 is a wasteful number, since it uses less digits than its factorization.

646491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 215500.

The product of its digits is 5184, while the sum is 30.

The square root of 646491 is about 804.0466404382. The cubic root of 646491 is about 86.4677505718.

It can be divided in two parts, 6464 and 91, that added together give a triangular number (6555 = T₁₁₄).

The spelling of 646491 in words is "six hundred forty-six thousand, four hundred ninety-one".