21221010001987 has 4 divisors (see below), whose sum is σ = 21221020252080. Its totient is φ = 21220999751896.

The previous prime is 21221010001897. The next prime is 21221010001999. The reversal of 21221010001987 is 78910001012212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21221010001987 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21221010001787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 806668 + ... + 6564505.

It is an arithmetic number, because the mean of its divisors is an integer number (5305255063020).

Almost surely, 2^{21221010001987} is an apocalyptic number.

21221010001987 is a deficient number, since it is larger than the sum of its proper divisors (10250093).

21221010001987 is an equidigital number, since it uses as much as digits as its factorization.

21221010001987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10250092.

The product of its (nonzero) digits is 4032, while the sum is 34.

The spelling of 21221010001987 in words is "twenty-one trillion, two hundred twenty-one billion, ten million, one thousand, nine hundred eighty-seven".