21640634563 has 2 divisors, whose sum is σ = 21640634564. Its totient is φ = 21640634562.

The previous prime is 21640634549. The next prime is 21640634567. The reversal of 21640634563 is 36543604612.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21640634563 - 2⁹ = 21640634051 is a prime.

It is not a weakly prime, because it can be changed into another prime (21640634567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10820317281 + 10820317282.

It is an arithmetic number, because the mean of its divisors is an integer number (10820317282).

Almost surely, 2^21640634563 is an apocalyptic number.

21640634563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21640634563 is an equidigital number, since it uses as much as digits as its factorization.

21640634563 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 311040, while the sum is 40.

The spelling of 21640634563 in words is "twenty-one billion, six hundred forty million, six hundred thirty-four thousand, five hundred sixty-three".