640212220 has 24 divisors (see below), whose sum is σ = 1415206800. Its totient is φ = 242606592.

The previous prime is 640212203. The next prime is 640212227. The reversal of 640212220 is 22212046.

It is a Harshad number since it is a multiple of its sum of digits (19).

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 polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 842005 + ... + 842764.

It is an arithmetic number, because the mean of its divisors is an integer number (58966950).

Almost surely, 2^640212220 is an apocalyptic number.

It is an amenable number.

640212220 is an abundant number, since it is smaller than the sum of its proper divisors (774994580).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640212220 is a wasteful number, since it uses less digits than its factorization.

640212220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1684797 (or 1684795 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 19.

The square root of 640212220 is about 25302.4152997298. The cubic root of 640212220 is about 861.8691184300.

Adding to 640212220 its reverse (22212046), we get a palindrome (662424266).

The spelling of 640212220 in words is "six hundred forty million, two hundred twelve thousand, two hundred twenty".