640521420 has 96 divisors (see below), whose sum is σ = 2236018176. Its totient is φ = 133094400.

The previous prime is 640521419. The next prime is 640521439. The reversal of 640521420 is 24125046.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 64701 + ... + 73940.

It is an arithmetic number, because the mean of its divisors is an integer number (23291856).

Almost surely, 2^640521420 is an apocalyptic number.

640521420 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

640521420 is an abundant number, since it is smaller than the sum of its proper divisors (1595496756).

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

640521420 is a wasteful number, since it uses less digits than its factorization.

640521420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 138671 (or 138669 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 24.

The square root of 640521420 is about 25308.5246507970. The cubic root of 640521420 is about 862.0078469291.

Adding to 640521420 its reverse (24125046), we get a palindrome (664646466).

The spelling of 640521420 in words is "six hundred forty million, five hundred twenty-one thousand, four hundred twenty".