640251505521 has 32 divisors (see below), whose sum is σ = 1005626048000. Its totient is φ = 401460195024.

The previous prime is 640251505433. The next prime is 640251505541. The reversal of 640251505521 is 125505152046.

640251505521 is a `hidden beast` number, since 6 + 4 + 0 + 2 + 51 + 50 + 552 + 1 = 666.

It is not a de Polignac number, because 640251505521 - 2²⁷ = 640117287793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640251505541) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4418095 + ... + 4560708.

It is an arithmetic number, because the mean of its divisors is an integer number (31425814000).

Almost surely, 2^640251505521 is an apocalyptic number.

It is an amenable number.

640251505521 is a deficient number, since it is larger than the sum of its proper divisors (365374542479).

640251505521 is a wasteful number, since it uses less digits than its factorization.

640251505521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8978970 (or 8978964 counting only the distinct ones).

The product of its (nonzero) digits is 60000, while the sum is 36.

Adding to 640251505521 its reverse (125505152046), we get a palindrome (765756657567).

The spelling of 640251505521 in words is "six hundred forty billion, two hundred fifty-one million, five hundred five thousand, five hundred twenty-one".