645992 has 8 divisors (see below), whose sum is σ = 1211250. Its totient is φ = 322992.

The previous prime is 645979. The next prime is 646003. The reversal of 645992 is 299546.

It can be written as a sum of positive squares in only one way, i.e., 401956 + 244036 = 634^2 + 494^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645992.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40367 + ... + 40382.

2⁶⁴⁵⁹⁹² is an apocalyptic number.

It is an amenable number.

645992 is a deficient number, since it is larger than the sum of its proper divisors (565258).

645992 is a wasteful number, since it uses less digits than its factorization.

645992 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80755 (or 80751 counting only the distinct ones).

The product of its digits is 19440, while the sum is 35.

The square root of 645992 is about 803.7362751550. The cubic root of 645992 is about 86.4454978704.

The spelling of 645992 in words is "six hundred forty-five thousand, nine hundred ninety-two".