640621669 has 2 divisors, whose sum is σ = 640621670. Its totient is φ = 640621668.

The previous prime is 640621649. The next prime is 640621717. The reversal of 640621669 is 966126046.

640621669 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 638219169 + 2402500 = 25263^2 + 1550^2 .

It is a cyclic number.

It is not a de Polignac number, because 640621669 - 2⁵ = 640621637 is a prime.

It is a super-2 number, since 2×640621669² = 820792245584691122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640621649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320310834 + 320310835.

It is an arithmetic number, because the mean of its divisors is an integer number (320310835).

Almost surely, 2^640621669 is an apocalyptic number.

It is an amenable number.

640621669 is a deficient number, since it is larger than the sum of its proper divisors (1).

640621669 is an equidigital number, since it uses as much as digits as its factorization.

640621669 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 93312, while the sum is 40.

The square root of 640621669 is about 25310.5051115145. The cubic root of 640621669 is about 862.0528159778.

The spelling of 640621669 in words is "six hundred forty million, six hundred twenty-one thousand, six hundred sixty-nine".