21365971871 has 2 divisors, whose sum is σ = 21365971872. Its totient is φ = 21365971870.

The previous prime is 21365971853. The next prime is 21365971889. The reversal of 21365971871 is 17817956312.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (21365971853) and next prime (21365971889).

It is a cyclic number.

It is not a de Polignac number, because 21365971871 - 2¹⁸ = 21365709727 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21365971171) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10682985935 + 10682985936.

It is an arithmetic number, because the mean of its divisors is an integer number (10682985936).

Almost surely, 2^21365971871 is an apocalyptic number.

21365971871 is a deficient number, since it is larger than the sum of its proper divisors (1).

21365971871 is an equidigital number, since it uses as much as digits as its factorization.

21365971871 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 635040, while the sum is 50.

The spelling of 21365971871 in words is "twenty-one billion, three hundred sixty-five million, nine hundred seventy-one thousand, eight hundred seventy-one".