211221009 has 6 divisors (see below), whose sum is σ = 305097026. Its totient is φ = 140814000.

The previous prime is 211220993. The next prime is 211221013. The reversal of 211221009 is 900122112.

211221009 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 209438784 + 1782225 = 14472^2 + 1335^2 .

It is not a de Polignac number, because 211221009 - 2⁴ = 211220993 is a prime.

It is a super-2 number, since 2×211221009² = 89228629285956162, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 211220982 and 211221000.

It is not an unprimeable number, because it can be changed into a prime (211221509) 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, 11734492 + ... + 11734509.

Almost surely, 2^211221009 is an apocalyptic number.

It is an amenable number.

211221009 is a deficient number, since it is larger than the sum of its proper divisors (93876017).

211221009 is a wasteful number, since it uses less digits than its factorization.

211221009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23469007 (or 23469004 counting only the distinct ones).

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

The square root of 211221009 is about 14533.4444988103. Note that the first 4 decimals coincide. The cubic root of 211221009 is about 595.5419669383.

The spelling of 211221009 in words is "two hundred eleven million, two hundred twenty-one thousand, nine".