21021020109 has 24 divisors (see below), whose sum is σ = 31119484032. Its totient is φ = 13667299200.

The previous prime is 21021020099. The next prime is 21021020117. The reversal of 21021020109 is 90102012012.

It is not a de Polignac number, because 21021020109 - 2⁵ = 21021020077 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21021020091 and 21021020100.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021020159) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 31909 + ... + 207509.

It is an arithmetic number, because the mean of its divisors is an integer number (1296645168).

Almost surely, 2^21021020109 is an apocalyptic number.

It is an amenable number.

21021020109 is a deficient number, since it is larger than the sum of its proper divisors (10098463923).

21021020109 is a wasteful number, since it uses less digits than its factorization.

21021020109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 175937 (or 175934 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 18.

The spelling of 21021020109 in words is "twenty-one billion, twenty-one million, twenty thousand, one hundred nine".