640919641 has 2 divisors, whose sum is σ = 640919642. Its totient is φ = 640919640.

The previous prime is 640919623. The next prime is 640919659. The reversal of 640919641 is 146919046.

It is a balanced prime because it is at equal distance from previous prime (640919623) and next prime (640919659).

It can be written as a sum of positive squares in only one way, i.e., 520798041 + 120121600 = 22821^2 + 10960^2 .

It is a cyclic number.

It is not a de Polignac number, because 640919641 - 2¹¹ = 640917593 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 640919594 and 640919603.

It is not a weakly prime, because it can be changed into another prime (640919681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320459820 + 320459821.

It is an arithmetic number, because the mean of its divisors is an integer number (320459821).

Almost surely, 2^640919641 is an apocalyptic number.

It is an amenable number.

640919641 is a deficient number, since it is larger than the sum of its proper divisors (1).

640919641 is an equidigital number, since it uses as much as digits as its factorization.

640919641 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 46656, while the sum is 40.

The square root of 640919641 is about 25316.3907577680. The cubic root of 640919641 is about 862.1864506428.

The spelling of 640919641 in words is "six hundred forty million, nine hundred nineteen thousand, six hundred forty-one".