645616042 has 4 divisors (see below), whose sum is σ = 968424066. Its totient is φ = 322808020.

The previous prime is 645616039. The next prime is 645616043. The reversal of 645616042 is 240616546.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 240616546 = 2 ⋅120308273.

It can be written as a sum of positive squares in only one way, i.e., 354606561 + 291009481 = 18831^2 + 17059^2 .

It is a junction number, because it is equal to n+sod(n) for n = 645615989 and 645616007.

It is not an unprimeable number, because it can be changed into a prime (645616043) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 161404009 + ... + 161404012.

Almost surely, 2^645616042 is an apocalyptic number.

645616042 is a deficient number, since it is larger than the sum of its proper divisors (322808024).

645616042 is a wasteful number, since it uses less digits than its factorization.

645616042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 322808023.

The product of its (nonzero) digits is 34560, while the sum is 34.

The square root of 645616042 is about 25408.9756188635. The cubic root of 645616042 is about 864.2872460623.

The spelling of 645616042 in words is "six hundred forty-five million, six hundred sixteen thousand, forty-two".