645531 has 8 divisors (see below), whose sum is σ = 869184. Its totient is φ = 426120.

The previous prime is 645529. The next prime is 645571. The reversal of 645531 is 135546.

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

It is not a de Polignac number, because 645531 - 2¹ = 645529 is a prime.

It is a super-2 number, since 2×645531² = 833420543922, which contains 22 as substring.

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

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 685 + ... + 1326.

It is an arithmetic number, because the mean of its divisors is an integer number (108648).

2⁶⁴⁵⁵³¹ is an apocalyptic number.

645531 is a deficient number, since it is larger than the sum of its proper divisors (223653).

645531 is a wasteful number, since it uses less digits than its factorization.

645531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2121.

The product of its digits is 1800, while the sum is 24.

The square root of 645531 is about 803.4494383594. The cubic root of 645531 is about 86.4249295775.

It can be divided in two parts, 645 and 531, that added together give a triangular number (1176 = T₄₈).

The spelling of 645531 in words is "six hundred forty-five thousand, five hundred thirty-one".