21020109 has 32 divisors (see below), whose sum is σ = 32814720. Its totient is φ = 11827200.

The previous prime is 21020093. The next prime is 21020117. The reversal of 21020109 is 90102012.

It is a happy number.

It is not a de Polignac number, because 21020109 - 2⁴ = 21020093 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020119) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 49719 + ... + 50139.

It is an arithmetic number, because the mean of its divisors is an integer number (1025460).

Almost surely, 2^21020109 is an apocalyptic number.

It is an amenable number.

21020109 is a deficient number, since it is larger than the sum of its proper divisors (11794611).

21020109 is a wasteful number, since it uses less digits than its factorization.

21020109 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 541.

The product of its (nonzero) digits is 36, while the sum is 15.

The square root of 21020109 is about 4584.7692417394. The cubic root of 21020109 is about 275.9804517766.

The spelling of 21020109 in words is "twenty-one million, twenty thousand, one hundred nine".