21420243221 has 8 divisors (see below), whose sum is σ = 23095994880. Its totient is φ = 19748497392.

The previous prime is 21420243193. The next prime is 21420243227. The reversal of 21420243221 is 12234202412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-21420243221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420243227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 990341 + ... + 1011738.

It is an arithmetic number, because the mean of its divisors is an integer number (2886999360).

Almost surely, 2^21420243221 is an apocalyptic number.

It is an amenable number.

21420243221 is a deficient number, since it is larger than the sum of its proper divisors (1675751659).

21420243221 is a wasteful number, since it uses less digits than its factorization.

21420243221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2002915.

The product of its (nonzero) digits is 1536, while the sum is 23.

Adding to 21420243221 its reverse (12234202412), we get a palindrome (33654445633).

The spelling of 21420243221 in words is "twenty-one billion, four hundred twenty million, two hundred forty-three thousand, two hundred twenty-one".