645994 has 4 divisors (see below), whose sum is σ = 968994. Its totient is φ = 322996.

The previous prime is 645979. The next prime is 646003. The reversal of 645994 is 499546.

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

It can be written as a sum of positive squares in only one way, i.e., 600625 + 45369 = 775^2 + 213^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161497 + ... + 161500.

2⁶⁴⁵⁹⁹⁴ is an apocalyptic number.

645994 is a deficient number, since it is larger than the sum of its proper divisors (323000).

645994 is a wasteful number, since it uses less digits than its factorization.

645994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322999.

The product of its digits is 38880, while the sum is 37.

The square root of 645994 is about 803.7375193432. The cubic root of 645994 is about 86.4455870824.

The spelling of 645994 in words is "six hundred forty-five thousand, nine hundred ninety-four".