21643289321 has 4 divisors (see below), whose sum is σ = 21659977812. Its totient is φ = 21626600832.

The previous prime is 21643289303. The next prime is 21643289351. The reversal of 21643289321 is 12398234612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11363560000 + 10279729321 = 106600^2 + 101389^2 .

It is a cyclic number.

It is not a de Polignac number, because 21643289321 - 2²² = 21639095017 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21643289351) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8342300 + ... + 8344893.

It is an arithmetic number, because the mean of its divisors is an integer number (5414994453).

Almost surely, 2^21643289321 is an apocalyptic number.

It is an amenable number.

21643289321 is a deficient number, since it is larger than the sum of its proper divisors (16688491).

21643289321 is a wasteful number, since it uses less digits than its factorization.

21643289321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16688490.

The product of its digits is 124416, while the sum is 41.

The spelling of 21643289321 in words is "twenty-one billion, six hundred forty-three million, two hundred eighty-nine thousand, three hundred twenty-one".