640434238731 has 24 divisors (see below), whose sum is σ = 1059666447840. Its totient is φ = 365117227776.

The previous prime is 640434238673. The next prime is 640434238739. The reversal of 640434238731 is 137832434046.

640434238731 is a `hidden beast` number, since 6 + 404 + 3 + 4 + 238 + 7 + 3 + 1 = 666.

It is not a de Polignac number, because 640434238731 - 2¹³ = 640434230539 is a prime.

It is a super-2 number, since 2×640434238731² (a number of 24 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (640434238739) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11711316 + ... + 11765873.

It is an arithmetic number, because the mean of its divisors is an integer number (44152768660).

Almost surely, 2^640434238731 is an apocalyptic number.

640434238731 is a deficient number, since it is larger than the sum of its proper divisors (419232209109).

640434238731 is a wasteful number, since it uses less digits than its factorization.

640434238731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23477635 (or 23477632 counting only the distinct ones).

The product of its (nonzero) digits is 1161216, while the sum is 45.

The spelling of 640434238731 in words is "six hundred forty billion, four hundred thirty-four million, two hundred thirty-eight thousand, seven hundred thirty-one".