21000198979 has 2 divisors, whose sum is σ = 21000198980. Its totient is φ = 21000198978.

The previous prime is 21000198959. The next prime is 21000199001. The reversal of 21000198979 is 97989100012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21000198979 is a prime.

It is not a weakly prime, because it can be changed into another prime (21000198949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500099489 + 10500099490.

It is an arithmetic number, because the mean of its divisors is an integer number (10500099490).

Almost surely, 2^21000198979 is an apocalyptic number.

21000198979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000198979 is an equidigital number, since it uses as much as digits as its factorization.

21000198979 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 81648, while the sum is 46.

The spelling of 21000198979 in words is "twenty-one billion, one hundred ninety-eight thousand, nine hundred seventy-nine".