640904443 has 2 divisors, whose sum is σ = 640904444. Its totient is φ = 640904442.

The previous prime is 640904399. The next prime is 640904483. The reversal of 640904443 is 344409046.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640904443 - 2¹³ = 640896251 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 640904399 and 640904408.

It is not a weakly prime, because it can be changed into another prime (640904483) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320452221 + 320452222.

It is an arithmetic number, because the mean of its divisors is an integer number (320452222).

Almost surely, 2^640904443 is an apocalyptic number.

640904443 is a deficient number, since it is larger than the sum of its proper divisors (1).

640904443 is an equidigital number, since it uses as much as digits as its factorization.

640904443 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 41472, while the sum is 34.

The square root of 640904443 is about 25316.0905947186. The cubic root of 640904443 is about 862.1796356370.

The spelling of 640904443 in words is "six hundred forty million, nine hundred four thousand, four hundred forty-three".