645651 has 12 divisors (see below), whose sum is σ = 967512. Its totient is φ = 430272.

The previous prime is 645649. The next prime is 645661. The reversal of 645651 is 156546.

It is a happy number.

645651 is a `hidden beast` number, since 6 + 4 + 5 + 651 = 666.

645651 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 645651 - 2¹ = 645649 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645651.

It is not an unprimeable number, because it can be changed into a prime (645611) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1086 + ... + 1571.

It is an arithmetic number, because the mean of its divisors is an integer number (80626).

2⁶⁴⁵⁶⁵¹ is an apocalyptic number.

645651 is a deficient number, since it is larger than the sum of its proper divisors (321861).

645651 is an equidigital number, since it uses as much as digits as its factorization.

645651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2672 (or 2660 counting only the distinct ones).

The product of its digits is 3600, while the sum is 27.

The square root of 645651 is about 803.5241128927. The cubic root of 645651 is about 86.4302845225.

It can be divided in two parts, 645 and 651, that added together give a 4-th power (1296 = 6⁴).

The spelling of 645651 in words is "six hundred forty-five thousand, six hundred fifty-one".