21561768959 has 2 divisors, whose sum is σ = 21561768960. Its totient is φ = 21561768958.

The previous prime is 21561768931. The next prime is 21561769039. The reversal of 21561768959 is 95986716512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21561768959 - 2⁸ = 21561768703 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21561768898 and 21561768907.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21561768929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10780884479 + 10780884480.

It is an arithmetic number, because the mean of its divisors is an integer number (10780884480).

Almost surely, 2^21561768959 is an apocalyptic number.

21561768959 is a deficient number, since it is larger than the sum of its proper divisors (1).

21561768959 is an equidigital number, since it uses as much as digits as its factorization.

21561768959 is an evil number, because the sum of its binary digits is even.

The product of its digits is 8164800, while the sum is 59.

The spelling of 21561768959 in words is "twenty-one billion, five hundred sixty-one million, seven hundred sixty-eight thousand, nine hundred fifty-nine".