640348921 has 2 divisors, whose sum is σ = 640348922. Its totient is φ = 640348920.

The previous prime is 640348897. The next prime is 640348931. The reversal of 640348921 is 129843046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 333573696 + 306775225 = 18264^2 + 17515^2 .

It is a cyclic number.

It is not a de Polignac number, because 640348921 - 2¹⁵ = 640316153 is a prime.

It is not a weakly prime, because it can be changed into another prime (640348931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320174460 + 320174461.

It is an arithmetic number, because the mean of its divisors is an integer number (320174461).

Almost surely, 2^640348921 is an apocalyptic number.

It is an amenable number.

640348921 is a deficient number, since it is larger than the sum of its proper divisors (1).

640348921 is an equidigital number, since it uses as much as digits as its factorization.

640348921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 41472, while the sum is 37.

The square root of 640348921 is about 25305.1164984475. The cubic root of 640348921 is about 861.9304574579.

The spelling of 640348921 in words is "six hundred forty million, three hundred forty-eight thousand, nine hundred twenty-one".