645542 has 4 divisors (see below), whose sum is σ = 968316. Its totient is φ = 322770.

The previous prime is 645529. The next prime is 645571. The reversal of 645542 is 245546.

It is a semiprime because it is the product of two primes.

It is an Ulam number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 645542.

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, 161384 + ... + 161387.

It is an arithmetic number, because the mean of its divisors is an integer number (242079).

2⁶⁴⁵⁵⁴² is an apocalyptic number.

645542 is a deficient number, since it is larger than the sum of its proper divisors (322774).

645542 is a wasteful number, since it uses less digits than its factorization.

645542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322773.

The product of its digits is 4800, while the sum is 26.

The square root of 645542 is about 803.4562838139. The cubic root of 645542 is about 86.4254204751.

The spelling of 645542 in words is "six hundred forty-five thousand, five hundred forty-two".