21021109979 has 2 divisors, whose sum is σ = 21021109980. Its totient is φ = 21021109978.

The previous prime is 21021109931. The next prime is 21021110029. The reversal of 21021109979 is 97990112012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021109979 is a prime.

It is not a weakly prime, because it can be changed into another prime (21021009979) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510554989 + 10510554990.

It is an arithmetic number, because the mean of its divisors is an integer number (10510554990).

Almost surely, 2^21021109979 is an apocalyptic number.

21021109979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021109979 is an equidigital number, since it uses as much as digits as its factorization.

21021109979 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20412, while the sum is 41.

The spelling of 21021109979 in words is "twenty-one billion, twenty-one million, one hundred nine thousand, nine hundred seventy-nine".