640378285 has 4 divisors (see below), whose sum is σ = 768453948. Its totient is φ = 512302624.

The previous prime is 640378267. The next prime is 640378289. The reversal of 640378285 is 582873046.

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

It can be written as a sum of positive squares in 2 ways, for example, as 349914436 + 290463849 = 18706^2 + 17043^2 .

It is a cyclic number.

It is not a de Polignac number, because 640378285 - 2¹¹ = 640376237 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640378289) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64037824 + ... + 64037833.

It is an arithmetic number, because the mean of its divisors is an integer number (192113487).

Almost surely, 2^640378285 is an apocalyptic number.

It is an amenable number.

640378285 is a deficient number, since it is larger than the sum of its proper divisors (128075663).

640378285 is a wasteful number, since it uses less digits than its factorization.

640378285 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128075662.

The product of its (nonzero) digits is 322560, while the sum is 43.

The square root of 640378285 is about 25305.6966906663. The cubic root of 640378285 is about 861.9436322226.

The spelling of 640378285 in words is "six hundred forty million, three hundred seventy-eight thousand, two hundred eighty-five".