21111020989 has 4 divisors (see below), whose sum is σ = 21838987260. Its totient is φ = 20383054720.

The previous prime is 21111020977. The next prime is 21111021013. The reversal of 21111020989 is 98902011112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8587172889 + 12523848100 = 92667^2 + 111910^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21111020989 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111020939) 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 in 3 ways as a sum of consecutive naturals, for example, 363983092 + ... + 363983149.

It is an arithmetic number, because the mean of its divisors is an integer number (5459746815).

Almost surely, 2^21111020989 is an apocalyptic number.

21111020989 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21111020989 is a deficient number, since it is larger than the sum of its proper divisors (727966271).

21111020989 is an equidigital number, since it uses as much as digits as its factorization.

21111020989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 727966270.

The product of its (nonzero) digits is 2592, while the sum is 34.

The spelling of 21111020989 in words is "twenty-one billion, one hundred eleven million, twenty thousand, nine hundred eighty-nine".