645986 has 8 divisors (see below), whose sum is σ = 1057104. Its totient is φ = 293620.

The previous prime is 645979. The next prime is 646003. The reversal of 645986 is 689546.

645986 = 99² + 100² + ... + 142².

It is a sphenic number, since it is the product of 3 distinct primes.

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 in 3 ways as a sum of consecutive naturals, for example, 14660 + ... + 14703.

It is an arithmetic number, because the mean of its divisors is an integer number (132138).

2⁶⁴⁵⁹⁸⁶ is an apocalyptic number.

645986 is a deficient number, since it is larger than the sum of its proper divisors (411118).

645986 is a wasteful number, since it uses less digits than its factorization.

645986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29376.

The product of its digits is 51840, while the sum is 38.

The square root of 645986 is about 803.7325425787. The cubic root of 645986 is about 86.4452302331.

The spelling of 645986 in words is "six hundred forty-five thousand, nine hundred eighty-six".