21055540643 has 2 divisors, whose sum is σ = 21055540644. Its totient is φ = 21055540642.

The previous prime is 21055540607. The next prime is 21055540651. The reversal of 21055540643 is 34604555012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21055540643 - 2¹⁰ = 21055539619 is a prime.

It is not a weakly prime, because it can be changed into another prime (21055540843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10527770321 + 10527770322.

It is an arithmetic number, because the mean of its divisors is an integer number (10527770322).

Almost surely, 2^21055540643 is an apocalyptic number.

21055540643 is a deficient number, since it is larger than the sum of its proper divisors (1).

21055540643 is an equidigital number, since it uses as much as digits as its factorization.

21055540643 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72000, while the sum is 35.

The spelling of 21055540643 in words is "twenty-one billion, fifty-five million, five hundred forty thousand, six hundred forty-three".