21221420209 has 4 divisors (see below), whose sum is σ = 23150640240. Its totient is φ = 19292200180.

The previous prime is 21221420191. The next prime is 21221420273. The reversal of 21221420209 is 90202412212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21221420209 - 2⁵ = 21221420177 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21221420299) 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 3 ways as a sum of consecutive naturals, for example, 964609999 + ... + 964610020.

It is an arithmetic number, because the mean of its divisors is an integer number (5787660060).

Almost surely, 2^21221420209 is an apocalyptic number.

It is an amenable number.

21221420209 is a deficient number, since it is larger than the sum of its proper divisors (1929220031).

21221420209 is a wasteful number, since it uses less digits than its factorization.

21221420209 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1929220030.

The product of its (nonzero) digits is 1152, while the sum is 25.

The spelling of 21221420209 in words is "twenty-one billion, two hundred twenty-one million, four hundred twenty thousand, two hundred nine".