645996 has 48 divisors (see below), whose sum is σ = 1679328. Its totient is φ = 192000.

The previous prime is 645979. The next prime is 646003. The reversal of 645996 is 699546.

It is a Harshad number since it is a multiple of its sum of digits (39).

Its product of digits (58320) is a multiple of the sum of its prime factors (162).

It is an unprimeable number.

645996 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6346 + ... + 6446.

It is an arithmetic number, because the mean of its divisors is an integer number (34986).

2⁶⁴⁵⁹⁹⁶ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 645996, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (839664).

645996 is an abundant number, since it is smaller than the sum of its proper divisors (1033332).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

645996 is a wasteful number, since it uses less digits than its factorization.

645996 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 162 (or 160 counting only the distinct ones).

The product of its digits is 58320, while the sum is 39.

The square root of 645996 is about 803.7387635295. The cubic root of 645996 is about 86.4456762943.

It can be divided in two parts, 6459 and 96, that added together give a triangular number (6555 = T₁₁₄).

The spelling of 645996 in words is "six hundred forty-five thousand, nine hundred ninety-six".