21211220009 has 6 divisors (see below), whose sum is σ = 24674276394. Its totient is φ = 18181045680.

The previous prime is 21211219973. The next prime is 21211220021. The reversal of 21211220009 is 90002211212.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21207514384 + 3705625 = 145628^2 + 1925^2 .

It is not a de Polignac number, because 21211220009 - 2²⁸ = 20942784553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21211220039) 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 5 ways as a sum of consecutive naturals, for example, 216440972 + ... + 216441069.

It is an arithmetic number, because the mean of its divisors is an integer number (4112379399).

Almost surely, 2^21211220009 is an apocalyptic number.

It is an amenable number.

21211220009 is a deficient number, since it is larger than the sum of its proper divisors (3463056385).

21211220009 is an equidigital number, since it uses as much as digits as its factorization.

21211220009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 432882055 (or 432882048 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 20.

The spelling of 21211220009 in words is "twenty-one billion, two hundred eleven million, two hundred twenty thousand, nine".