21101021987 has 2 divisors, whose sum is σ = 21101021988. Its totient is φ = 21101021986.

The previous prime is 21101021971. The next prime is 21101022011. The reversal of 21101021987 is 78912010112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21101021987 - 2⁴ = 21101021971 is a prime.

It is not a weakly prime, because it can be changed into another prime (21101021927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550510993 + 10550510994.

It is an arithmetic number, because the mean of its divisors is an integer number (10550510994).

Almost surely, 2^21101021987 is an apocalyptic number.

21101021987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21101021987 is an equidigital number, since it uses as much as digits as its factorization.

21101021987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2016, while the sum is 32.

The spelling of 21101021987 in words is "twenty-one billion, one hundred one million, twenty-one thousand, nine hundred eighty-seven".