640661513 has 8 divisors (see below), whose sum is σ = 675381600. Its totient is φ = 606041568.

The previous prime is 640661501. The next prime is 640661519. The reversal of 640661513 is 315166046.

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

It is a cyclic number.

It is not a de Polignac number, because 640661513 - 2¹⁴ = 640645129 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640661513.

It is not an unprimeable number, because it can be changed into a prime (640661519) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11708 + ... + 37661.

It is an arithmetic number, because the mean of its divisors is an integer number (84422700).

Almost surely, 2^640661513 is an apocalyptic number.

It is an amenable number.

640661513 is a deficient number, since it is larger than the sum of its proper divisors (34720087).

640661513 is a wasteful number, since it uses less digits than its factorization.

640661513 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50071.

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 640661513 is about 25311.2922032835. The cubic root of 640661513 is about 862.0706876390.

The spelling of 640661513 in words is "six hundred forty million, six hundred sixty-one thousand, five hundred thirteen".