21540603641 has 2 divisors, whose sum is σ = 21540603642. Its totient is φ = 21540603640.

The previous prime is 21540603619. The next prime is 21540603647. The reversal of 21540603641 is 14630604512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21375609616 + 164994025 = 146204^2 + 12845^2 .

It is a cyclic number.

It is not a de Polignac number, because 21540603641 - 2¹⁸ = 21540341497 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21540603598 and 21540603607.

It is not a weakly prime, because it can be changed into another prime (21540603647) 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, 10770301820 + 10770301821.

It is an arithmetic number, because the mean of its divisors is an integer number (10770301821).

Almost surely, 2^21540603641 is an apocalyptic number.

It is an amenable number.

21540603641 is a deficient number, since it is larger than the sum of its proper divisors (1).

21540603641 is an equidigital number, since it uses as much as digits as its factorization.

21540603641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 17280, while the sum is 32.

The spelling of 21540603641 in words is "twenty-one billion, five hundred forty million, six hundred three thousand, six hundred forty-one".