640434431 has 16 divisors (see below), whose sum is σ = 789096000. Its totient is φ = 506158848.

The previous prime is 640434427. The next prime is 640434437. The reversal of 640434431 is 134434046.

640434431 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 640434431 - 2² = 640434427 is a prime.

It is a super-2 number, since 2×640434431² = 820312520820587522, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 640434394 and 640434403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640434437) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 92105 + ... + 98813.

It is an arithmetic number, because the mean of its divisors is an integer number (49318500).

Almost surely, 2^640434431 is an apocalyptic number.

640434431 is a deficient number, since it is larger than the sum of its proper divisors (148661569).

640434431 is a wasteful number, since it uses less digits than its factorization.

640434431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7778.

The product of its (nonzero) digits is 13824, while the sum is 29.

The square root of 640434431 is about 25306.8060213058. The cubic root of 640434431 is about 861.9688221632.

Adding to 640434431 its reverse (134434046), we get a palindrome (774868477).

The spelling of 640434431 in words is "six hundred forty million, four hundred thirty-four thousand, four hundred thirty-one".