21121002009 has 6 divisors (see below), whose sum is σ = 30508114026. Its totient is φ = 14080668000.

The previous prime is 21121001969. The next prime is 21121002029. The reversal of 21121002009 is 90020012112.

It can be written as a sum of positive squares in only one way, i.e., 20391840000 + 729162009 = 142800^2 + 27003^2 .

It is not a de Polignac number, because 21121002009 - 2⁹ = 21121001497 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21121001982 and 21121002000.

It is not an unprimeable number, because it can be changed into a prime (21121002029) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1173388992 + ... + 1173389009.

It is an arithmetic number, because the mean of its divisors is an integer number (5084685671).

Almost surely, 2^21121002009 is an apocalyptic number.

It is an amenable number.

21121002009 is a deficient number, since it is larger than the sum of its proper divisors (9387112017).

21121002009 is a wasteful number, since it uses less digits than its factorization.

21121002009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2346778007 (or 2346778004 counting only the distinct ones).

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

The spelling of 21121002009 in words is "twenty-one billion, one hundred twenty-one million, two thousand, nine".