640306081 has 8 divisors (see below), whose sum is σ = 652875624. Its totient is φ = 627803520.

The previous prime is 640306067. The next prime is 640306097. The reversal of 640306081 is 180603046.

It can be written as a sum of positive squares in 4 ways, for example, as 63345681 + 576960400 = 7959^2 + 24020^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640306081 - 2⁵ = 640306049 is a prime.

It is a super-2 number, since 2×640306081² = 819983754731157122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640306031) 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 7 ways as a sum of consecutive naturals, for example, 2781 + ... + 35893.

It is an arithmetic number, because the mean of its divisors is an integer number (81609453).

Almost surely, 2^640306081 is an apocalyptic number.

640306081 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

640306081 is a deficient number, since it is larger than the sum of its proper divisors (12569543).

640306081 is a wasteful number, since it uses less digits than its factorization.

640306081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33491.

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 640306081 is about 25304.2700151575. The cubic root of 640306081 is about 861.9112356852.

The spelling of 640306081 in words is "six hundred forty million, three hundred six thousand, eighty-one".