640616906 has 8 divisors (see below), whose sum is σ = 970832100. Its totient is φ = 317006208.

The previous prime is 640616903. The next prime is 640616959. The reversal of 640616906 is 609616046.

It can be written as a sum of positive squares in 2 ways, for example, as 577969681 + 62647225 = 24041^2 + 7915^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 640616906.

It is not an unprimeable number, because it can be changed into a prime (640616903) 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, 1650881 + ... + 1651268.

Almost surely, 2^640616906 is an apocalyptic number.

640616906 is a deficient number, since it is larger than the sum of its proper divisors (330215194).

640616906 is a wasteful number, since it uses less digits than its factorization.

640616906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3302248.

The product of its (nonzero) digits is 46656, while the sum is 38.

The square root of 640616906 is about 25310.4110199736. The cubic root of 640616906 is about 862.0506795282.

The spelling of 640616906 in words is "six hundred forty million, six hundred sixteen thousand, nine hundred six".