640212221 has 16 divisors (see below), whose sum is σ = 720137088. Its totient is φ = 564033600.

The previous prime is 640212203. The next prime is 640212227. The reversal of 640212221 is 122212046.

It is a happy number.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640212221 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 640212193 and 640212202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640212227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 104051 + ... + 110031.

It is an arithmetic number, because the mean of its divisors is an integer number (45008568).

Almost surely, 2^640212221 is an apocalyptic number.

It is an amenable number.

640212221 is a deficient number, since it is larger than the sum of its proper divisors (79924867).

640212221 is a wasteful number, since it uses less digits than its factorization.

640212221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6292.

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

The square root of 640212221 is about 25302.4153194907. The cubic root of 640212221 is about 861.8691188787.

Adding to 640212221 its reverse (122212046), we get a palindrome (762424267).

The spelling of 640212221 in words is "six hundred forty million, two hundred twelve thousand, two hundred twenty-one".