21221101209 has 64 divisors (see below), whose sum is σ = 35648667648. Its totient is φ = 10908206400.

The previous prime is 21221101201. The next prime is 21221101211. The reversal of 21221101209 is 90210112212.

It is not a de Polignac number, because 21221101209 - 2³ = 21221101201 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21221101201) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 13404832 + ... + 13406414.

It is an arithmetic number, because the mean of its divisors is an integer number (557010432).

Almost surely, 2^21221101209 is an apocalyptic number.

It is an amenable number.

21221101209 is a deficient number, since it is larger than the sum of its proper divisors (14427566439).

21221101209 is a wasteful number, since it uses less digits than its factorization.

21221101209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2178.

The product of its (nonzero) digits is 144, while the sum is 21.

The spelling of 21221101209 in words is "twenty-one billion, two hundred twenty-one million, one hundred one thousand, two hundred nine".