640609538 has 12 divisors (see below), whose sum is σ = 1020764562. Its totient is φ = 301463040.

The previous prime is 640609531. The next prime is 640609549. The reversal of 640609538 is 835906046.

It can be written as a sum of positive squares in 3 ways, for example, as 624150289 + 16459249 = 24983^2 + 4057^2 .

It is a junction number, because it is equal to n+sod(n) for n = 640609495 and 640609504.

It is not an unprimeable number, because it can be changed into a prime (640609531) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 553583 + ... + 554738.

Almost surely, 2^640609538 is an apocalyptic number.

640609538 is a deficient number, since it is larger than the sum of its proper divisors (380155024).

640609538 is a wasteful number, since it uses less digits than its factorization.

640609538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1108357 (or 1108340 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 41.

The square root of 640609538 is about 25310.2654668022. The cubic root of 640609538 is about 862.0473745817.

The spelling of 640609538 in words is "six hundred forty million, six hundred nine thousand, five hundred thirty-eight".