21102020987 has 2 divisors, whose sum is σ = 21102020988. Its totient is φ = 21102020986.

The previous prime is 21102020981. The next prime is 21102021019. The reversal of 21102020987 is 78902020112.

It is a happy number.

It is an a-pointer prime, because the next prime (21102021019) can be obtained adding 21102020987 to its sum of digits (32).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21102020987 - 2⁴ = 21102020971 is a prime.

It is not a weakly prime, because it can be changed into another prime (21102020981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10551010493 + 10551010494.

It is an arithmetic number, because the mean of its divisors is an integer number (10551010494).

Almost surely, 2^21102020987 is an apocalyptic number.

21102020987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21102020987 is an equidigital number, since it uses as much as digits as its factorization.

21102020987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 32.

The spelling of 21102020987 in words is "twenty-one billion, one hundred two million, twenty thousand, nine hundred eighty-seven".