21005918827 has 2 divisors, whose sum is σ = 21005918828. Its totient is φ = 21005918826.

The previous prime is 21005918809. The next prime is 21005918833. The reversal of 21005918827 is 72881950012.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21005918827 - 2¹¹ = 21005916779 is a prime.

It is not a weakly prime, because it can be changed into another prime (21005918807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502959413 + 10502959414.

It is an arithmetic number, because the mean of its divisors is an integer number (10502959414).

Almost surely, 2^21005918827 is an apocalyptic number.

21005918827 is a deficient number, since it is larger than the sum of its proper divisors (1).

21005918827 is an equidigital number, since it uses as much as digits as its factorization.

21005918827 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 80640, while the sum is 43.

The spelling of 21005918827 in words is "twenty-one billion, five million, nine hundred eighteen thousand, eight hundred twenty-seven".