21640930643 has 2 divisors, whose sum is σ = 21640930644. Its totient is φ = 21640930642.

The previous prime is 21640930627. The next prime is 21640930747. The reversal of 21640930643 is 34603904612.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21640930643 - 2⁴ = 21640930627 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21640930597 and 21640930606.

It is not a weakly prime, because it can be changed into another prime (21640938643) 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, 10820465321 + 10820465322.

It is an arithmetic number, because the mean of its divisors is an integer number (10820465322).

Almost surely, 2^21640930643 is an apocalyptic number.

21640930643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21640930643 is an equidigital number, since it uses as much as digits as its factorization.

21640930643 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 38.

The spelling of 21640930643 in words is "twenty-one billion, six hundred forty million, nine hundred thirty thousand, six hundred forty-three".