21001998443 has 2 divisors, whose sum is σ = 21001998444. Its totient is φ = 21001998442.

The previous prime is 21001998427. The next prime is 21001998463. The reversal of 21001998443 is 34489910012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21001998443 - 2⁴ = 21001998427 is a prime.

It is a Sophie Germain prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21001998443.

It is not a weakly prime, because it can be changed into another prime (21001998463) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500999221 + 10500999222.

It is an arithmetic number, because the mean of its divisors is an integer number (10500999222).

Almost surely, 2^21001998443 is an apocalyptic number.

21001998443 is a deficient number, since it is larger than the sum of its proper divisors (1).

21001998443 is an equidigital number, since it uses as much as digits as its factorization.

21001998443 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 62208, while the sum is 41.

The spelling of 21001998443 in words is "twenty-one billion, one million, nine hundred ninety-eight thousand, four hundred forty-three".