640224421 has 4 divisors (see below), whose sum is σ = 640972332. Its totient is φ = 639476512.

The previous prime is 640224419. The next prime is 640224433. The reversal of 640224421 is 124422046.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 377330625 + 262893796 = 19425^2 + 16214^2 .

It is a cyclic number.

It is not a de Polignac number, because 640224421 - 2¹ = 640224419 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640224461) 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, 372670 + ... + 374383.

It is an arithmetic number, because the mean of its divisors is an integer number (160243083).

Almost surely, 2^640224421 is an apocalyptic number.

It is an amenable number.

640224421 is a deficient number, since it is larger than the sum of its proper divisors (747911).

640224421 is an equidigital number, since it uses as much as digits as its factorization.

640224421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 747910.

The product of its (nonzero) digits is 3072, while the sum is 25.

The square root of 640224421 is about 25302.6564020460. The cubic root of 640224421 is about 861.8745934886.

Adding to 640224421 its reverse (124422046), we get a palindrome (764646467).

The spelling of 640224421 in words is "six hundred forty million, two hundred twenty-four thousand, four hundred twenty-one".