21102021009 has 6 divisors (see below), whose sum is σ = 30480697026. Its totient is φ = 14068014000.

The previous prime is 21102020987. The next prime is 21102021019. The reversal of 21102021009 is 90012020112.

It can be written as a sum of positive squares in only one way, i.e., 11151360000 + 9950661009 = 105600^2 + 99753^2 .

It is not a de Polignac number, because 21102021009 - 2⁹ = 21102020497 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21102020982 and 21102021000.

It is not an unprimeable number, because it can be changed into a prime (21102021019) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1172334492 + ... + 1172334509.

It is an arithmetic number, because the mean of its divisors is an integer number (5080116171).

Almost surely, 2^21102021009 is an apocalyptic number.

It is an amenable number.

21102021009 is a deficient number, since it is larger than the sum of its proper divisors (9378676017).

21102021009 is a wasteful number, since it uses less digits than its factorization.

21102021009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2344669007 (or 2344669004 counting only the distinct ones).

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

The spelling of 21102021009 in words is "twenty-one billion, one hundred two million, twenty-one thousand, nine".