20993611643 has 2 divisors, whose sum is σ = 20993611644. Its totient is φ = 20993611642.

The previous prime is 20993611631. The next prime is 20993611657. The reversal of 20993611643 is 34611639902.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20993611643 - 2⁶ = 20993611579 is a prime.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 20993611594 and 20993611603.

It is not a weakly prime, because it can be changed into another prime (20993691643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10496805821 + 10496805822.

It is an arithmetic number, because the mean of its divisors is an integer number (10496805822).

Almost surely, 2^20993611643 is an apocalyptic number.

20993611643 is a deficient number, since it is larger than the sum of its proper divisors (1).

20993611643 is an equidigital number, since it uses as much as digits as its factorization.

20993611643 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 209952, while the sum is 44.

The spelling of 20993611643 in words is "twenty billion, nine hundred ninety-three million, six hundred eleven thousand, six hundred forty-three".