640335431 has 4 divisors (see below), whose sum is σ = 657641832. Its totient is φ = 623029032.

The previous prime is 640335419. The next prime is 640335461. The reversal of 640335431 is 134533046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 134533046 = 2 ⋅67266523.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640335431 is a prime.

It is a super-2 number, since 2×640335431² = 820058928387911522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 640335394 and 640335403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640335461) 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, 8653145 + ... + 8653218.

It is an arithmetic number, because the mean of its divisors is an integer number (164410458).

Almost surely, 2^640335431 is an apocalyptic number.

640335431 is a deficient number, since it is larger than the sum of its proper divisors (17306401).

640335431 is a wasteful number, since it uses less digits than its factorization.

640335431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17306400.

The product of its (nonzero) digits is 12960, while the sum is 29.

The square root of 640335431 is about 25304.8499501578. The cubic root of 640335431 is about 861.9244047559.

Adding to 640335431 its reverse (134533046), we get a palindrome (774868477).

The spelling of 640335431 in words is "six hundred forty million, three hundred thirty-five thousand, four hundred thirty-one".