21351016987 has 2 divisors, whose sum is σ = 21351016988. Its totient is φ = 21351016986.

The previous prime is 21351016957. The next prime is 21351016991. The reversal of 21351016987 is 78961015312.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21351016987 is a prime.

It is not a weakly prime, because it can be changed into another prime (21351016957) 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, 10675508493 + 10675508494.

It is an arithmetic number, because the mean of its divisors is an integer number (10675508494).

Almost surely, 2^21351016987 is an apocalyptic number.

21351016987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21351016987 is an equidigital number, since it uses as much as digits as its factorization.

21351016987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 90720, while the sum is 43.

The spelling of 21351016987 in words is "twenty-one billion, three hundred fifty-one million, sixteen thousand, nine hundred eighty-seven".