21001220999987 has 2 divisors, whose sum is σ = 21001220999988. Its totient is φ = 21001220999986.

The previous prime is 21001220999981. The next prime is 21001221000031. The reversal of 21001220999987 is 78999902210012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21001220999987 - 2¹⁸ = 21001220737843 is a prime.

It is not a weakly prime, because it can be changed into another prime (21001220999981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500610499993 + 10500610499994.

It is an arithmetic number, because the mean of its divisors is an integer number (10500610499994).

Almost surely, 2^{21001220999987} is an apocalyptic number.

21001220999987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001220999987 is an equidigital number, since it uses as much as digits as its factorization.

21001220999987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2939328, while the sum is 59.

The spelling of 21001220999987 in words is "twenty-one trillion, one billion, two hundred twenty million, nine hundred ninety-nine thousand, nine hundred eighty-seven".