640134921 has 8 divisors (see below), whose sum is σ = 857241280. Its totient is φ = 424892592.

The previous prime is 640134907. The next prime is 640134923. The reversal of 640134921 is 129431046.

640134921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 640134921 - 2⁶ = 640134857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640134923) 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, 465205 + ... + 466578.

It is an arithmetic number, because the mean of its divisors is an integer number (107155160).

Almost surely, 2^640134921 is an apocalyptic number.

It is an amenable number.

640134921 is a deficient number, since it is larger than the sum of its proper divisors (217106359).

640134921 is a wasteful number, since it uses less digits than its factorization.

640134921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 932015.

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 640134921 is about 25300.8877512233. The cubic root of 640134921 is about 861.8344297750.

Adding to 640134921 its reverse (129431046), we get a palindrome (769565967).

The spelling of 640134921 in words is "six hundred forty million, one hundred thirty-four thousand, nine hundred twenty-one".