21009999999887 has 2 divisors, whose sum is σ = 21009999999888. Its totient is φ = 21009999999886.

The previous prime is 21009999999883. The next prime is 21009999999931. The reversal of 21009999999887 is 78899999990012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21009999999887 - 2² = 21009999999883 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21009999999883) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504999999943 + 10504999999944.

It is an arithmetic number, because the mean of its divisors is an integer number (10504999999944).

Almost surely, 2^{21009999999887} is an apocalyptic number.

21009999999887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21009999999887 is an equidigital number, since it uses as much as digits as its factorization.

21009999999887 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4285540224, while the sum is 89.

The spelling of 21009999999887 in words is "twenty-one trillion, nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, eight hundred eighty-seven".