645251 has 4 divisors (see below), whose sum is σ = 647904. Its totient is φ = 642600.

The previous prime is 645233. The next prime is 645257. The reversal of 645251 is 152546.

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

It is a cyclic number.

It is not a de Polignac number, because 645251 - 2⁶ = 645187 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645251.

It is not an unprimeable number, because it can be changed into a prime (645257) 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, 920 + ... + 1461.

It is an arithmetic number, because the mean of its divisors is an integer number (161976).

2⁶⁴⁵²⁵¹ is an apocalyptic number.

645251 is a deficient number, since it is larger than the sum of its proper divisors (2653).

645251 is a wasteful number, since it uses less digits than its factorization.

645251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2652.

The product of its digits is 1200, while the sum is 23.

The square root of 645251 is about 803.2751707852. The cubic root of 645251 is about 86.4124321245.

Adding to 645251 its reverse (152546), we get a palindrome (797797).

The spelling of 645251 in words is "six hundred forty-five thousand, two hundred fifty-one".