645842 has 4 divisors (see below), whose sum is σ = 968766. Its totient is φ = 322920.

The previous prime is 645839. The next prime is 645851. The reversal of 645842 is 248546.

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., 516961 + 128881 = 719^2 + 359^2 .

It is a super-2 number, since 2×645842² = 834223777928, which contains 22 as substring.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645842.

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, 161459 + ... + 161462.

2⁶⁴⁵⁸⁴² is an apocalyptic number.

645842 is a deficient number, since it is larger than the sum of its proper divisors (322924).

645842 is a wasteful number, since it uses less digits than its factorization.

645842 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322923.

The product of its digits is 7680, while the sum is 29.

The square root of 645842 is about 803.6429555468. The cubic root of 645842 is about 86.4388064416.

The spelling of 645842 in words is "six hundred forty-five thousand, eight hundred forty-two".