640638238733 has 4 divisors (see below), whose sum is σ = 640639874400. Its totient is φ = 640636603068.

The previous prime is 640638238717. The next prime is 640638238739. The reversal of 640638238733 is 337832836046.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 640638238733 - 2⁴ = 640638238717 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 (640638238739) 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, 156968 + ... + 1142766.

It is an arithmetic number, because the mean of its divisors is an integer number (160159968600).

Almost surely, 2^640638238733 is an apocalyptic number.

It is an amenable number.

640638238733 is a deficient number, since it is larger than the sum of its proper divisors (1635667).

640638238733 is an equidigital number, since it uses as much as digits as its factorization.

640638238733 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1635666.

The product of its (nonzero) digits is 10450944, while the sum is 53.

The spelling of 640638238733 in words is "six hundred forty billion, six hundred thirty-eight million, two hundred thirty-eight thousand, seven hundred thirty-three".