640699 has 4 divisors (see below), whose sum is σ = 674440. Its totient is φ = 606960.

The previous prime is 640691. The next prime is 640727. The reversal of 640699 is 996046.

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

It is a cyclic number.

It is not a de Polignac number, because 640699 - 2³ = 640691 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640691) 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, 16842 + ... + 16879.

It is an arithmetic number, because the mean of its divisors is an integer number (168610).

2⁶⁴⁰⁶⁹⁹ is an apocalyptic number.

640699 is a deficient number, since it is larger than the sum of its proper divisors (33741).

640699 is a wasteful number, since it uses less digits than its factorization.

640699 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33740.

The product of its (nonzero) digits is 11664, while the sum is 34.

The square root of 640699 is about 800.4367557777. The cubic root of 640699 is about 86.2087501413.

The spelling of 640699 in words is "six hundred forty thousand, six hundred ninety-nine".