21043111987 has 2 divisors, whose sum is σ = 21043111988. Its totient is φ = 21043111986.

The previous prime is 21043111937. The next prime is 21043112011. The reversal of 21043111987 is 78911134012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21043111987 is a prime.

It is not a weakly prime, because it can be changed into another prime (21043111937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10521555993 + 10521555994.

It is an arithmetic number, because the mean of its divisors is an integer number (10521555994).

Almost surely, 2^21043111987 is an apocalyptic number.

21043111987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21043111987 is an equidigital number, since it uses as much as digits as its factorization.

21043111987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 37.

Adding to 21043111987 its reverse (78911134012), we get a palindrome (99954245999).

The spelling of 21043111987 in words is "twenty-one billion, forty-three million, one hundred eleven thousand, nine hundred eighty-seven".