645997 has 4 divisors (see below), whose sum is σ = 704736. Its totient is φ = 587260.

The previous prime is 645979. The next prime is 646003. The reversal of 645997 is 799546.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 645997 - 2¹¹ = 643949 is a prime.

It is a Duffinian number.

It is a plaindrome in base 8.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29353 + ... + 29374.

It is an arithmetic number, because the mean of its divisors is an integer number (176184).

2⁶⁴⁵⁹⁹⁷ is an apocalyptic number.

It is an amenable number.

645997 is a deficient number, since it is larger than the sum of its proper divisors (58739).

645997 is a wasteful number, since it uses less digits than its factorization.

645997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 58738.

The product of its digits is 68040, while the sum is 40.

The square root of 645997 is about 803.7393856220. The cubic root of 645997 is about 86.4457209002.

It can be divided in two parts, 6459 and 97, that added together give a palindrome (6556).

The spelling of 645997 in words is "six hundred forty-five thousand, nine hundred ninety-seven".