640559999 has 4 divisors (see below), whose sum is σ = 650120664. Its totient is φ = 630999336.

The previous prime is 640559993. The next prime is 640560047. The reversal of 640559999 is 999955046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 999955046 = 2 ⋅499977523.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640559999 is a prime.

It is a super-2 number, since 2×640559999² = 820634224637760002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640559993) 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, 4780232 + ... + 4780365.

It is an arithmetic number, because the mean of its divisors is an integer number (162530166).

Almost surely, 2^640559999 is an apocalyptic number.

640559999 is a deficient number, since it is larger than the sum of its proper divisors (9560665).

640559999 is an equidigital number, since it uses as much as digits as its factorization.

640559999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9560664.

The product of its (nonzero) digits is 3936600, while the sum is 56.

The square root of 640559999 is about 25309.2868133419. The cubic root of 640559999 is about 862.0251530030.

The spelling of 640559999 in words is "six hundred forty million, five hundred fifty-nine thousand, nine hundred ninety-nine".