21853459921 has 4 divisors (see below), whose sum is σ = 21863688292. Its totient is φ = 21843231552.

The previous prime is 21853459891. The next prime is 21853459939. The reversal of 21853459921 is 12995435812.

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 9374112400 + 12479347521 = 96820^2 + 111711^2 .

It is a cyclic number.

It is not a de Polignac number, because 21853459921 - 2⁹ = 21853459409 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21853457921) 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, 5110980 + ... + 5115253.

It is an arithmetic number, because the mean of its divisors is an integer number (5465922073).

Almost surely, 2^21853459921 is an apocalyptic number.

It is an amenable number.

21853459921 is a deficient number, since it is larger than the sum of its proper divisors (10228371).

21853459921 is a wasteful number, since it uses less digits than its factorization.

21853459921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10228370.

The product of its digits is 777600, while the sum is 49.

The spelling of 21853459921 in words is "twenty-one billion, eight hundred fifty-three million, four hundred fifty-nine thousand, nine hundred twenty-one".