645231 has 4 divisors (see below), whose sum is σ = 860312. Its totient is φ = 430152.

The previous prime is 645187. The next prime is 645233. The reversal of 645231 is 132546.

It is a happy number.

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

It is not a de Polignac number, because 645231 - 2¹¹ = 643183 is a prime.

It is a super-2 number, since 2×645231² = 832646086722, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 645198 and 645207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645233) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107536 + ... + 107541.

It is an arithmetic number, because the mean of its divisors is an integer number (215078).

2⁶⁴⁵²³¹ is an apocalyptic number.

645231 is a deficient number, since it is larger than the sum of its proper divisors (215081).

645231 is a wasteful number, since it uses less digits than its factorization.

645231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215080.

The product of its digits is 720, while the sum is 21.

The square root of 645231 is about 803.2627216546. The cubic root of 645231 is about 86.4115393110.

Adding to 645231 its reverse (132546), we get a palindrome (777777).

The spelling of 645231 in words is "six hundred forty-five thousand, two hundred thirty-one".