640420326 has 192 divisors, whose sum is σ = 1811496960. Its totient is φ = 158906880.

The previous prime is 640420321. The next prime is 640420331. The reversal of 640420326 is 623024046.

It is an interprime number because it is at equal distance from previous prime (640420321) and next prime (640420331).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 640420326.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640420321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3352891 + ... + 3353081.

It is an arithmetic number, because the mean of its divisors is an integer number (9434880).

Almost surely, 2^640420326 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640420326, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (905748480).

640420326 is an abundant number, since it is smaller than the sum of its proper divisors (1171076634).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640420326 is a wasteful number, since it uses less digits than its factorization.

640420326 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 331 (or 328 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 27.

The square root of 640420326 is about 25306.5273397991. The cubic root of 640420326 is about 861.9624940839.

The spelling of 640420326 in words is "six hundred forty million, four hundred twenty thousand, three hundred twenty-six".