640402211 has 4 divisors (see below), whose sum is σ = 640711152. Its totient is φ = 640093272.

The previous prime is 640402207. The next prime is 640402219. The reversal of 640402211 is 112204046.

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 640402211 - 2² = 640402207 is a prime.

It is a super-2 number, since 2×640402211² = 820229983707377042, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640402219) 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, 151340 + ... + 155513.

It is an arithmetic number, because the mean of its divisors is an integer number (160177788).

Almost surely, 2^640402211 is an apocalyptic number.

640402211 is a deficient number, since it is larger than the sum of its proper divisors (308941).

640402211 is a wasteful number, since it uses less digits than its factorization.

640402211 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 308940.

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 640402211 is about 25306.1694256559. The cubic root of 640402211 is about 861.9543668186.

Adding to 640402211 its reverse (112204046), we get a palindrome (752606257).

The spelling of 640402211 in words is "six hundred forty million, four hundred two thousand, two hundred eleven".