645511 has 4 divisors (see below), whose sum is σ = 667800. Its totient is φ = 623224.

The previous prime is 645503. The next prime is 645521. The reversal of 645511 is 115546.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 115546 = 2 ⋅57773.

It is a cyclic number.

It is not a de Polignac number, because 645511 - 2³ = 645503 is a prime.

It is a super-2 number, since 2×645511² = 833368902242, which contains 22 as substring.

It is a Duffinian number.

645511 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11101 + ... + 11158.

It is an arithmetic number, because the mean of its divisors is an integer number (166950).

2⁶⁴⁵⁵¹¹ is an apocalyptic number.

645511 is a deficient number, since it is larger than the sum of its proper divisors (22289).

645511 is a wasteful number, since it uses less digits than its factorization.

645511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22288.

The product of its digits is 600, while the sum is 22.

The square root of 645511 is about 803.4369919290. The cubic root of 645511 is about 86.4240370221.

It can be divided in two parts, 645 and 511, that added together give a square (1156 = 34²).

The spelling of 645511 in words is "six hundred forty-five thousand, five hundred eleven".