645938 has 4 divisors (see below), whose sum is σ = 968910. Its totient is φ = 322968.

The previous prime is 645937. The next prime is 645941. The reversal of 645938 is 839546.

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., 619369 + 26569 = 787^2 + 163^2 .

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 645898 and 645907.

It is not an unprimeable number, because it can be changed into a prime (645937) by changing a digit.

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, 161483 + ... + 161486.

2⁶⁴⁵⁹³⁸ is an apocalyptic number.

645938 is a deficient number, since it is larger than the sum of its proper divisors (322972).

645938 is a wasteful number, since it uses less digits than its factorization.

645938 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322971.

The product of its digits is 25920, while the sum is 35.

The square root of 645938 is about 803.7026813443. The cubic root of 645938 is about 86.4430890753.

The spelling of 645938 in words is "six hundred forty-five thousand, nine hundred thirty-eight".