21806981353 has 4 divisors (see below), whose sum is σ = 23089744980. Its totient is φ = 20524217728.

The previous prime is 21806981351. The next prime is 21806981411. The reversal of 21806981353 is 35318960812.

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 19455507289 + 2351474064 = 139483^2 + 48492^2 .

It is a cyclic number.

It is not a de Polignac number, because 21806981353 - 2¹ = 21806981351 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21806981351) 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, 641381788 + ... + 641381821.

It is an arithmetic number, because the mean of its divisors is an integer number (5772436245).

Almost surely, 2^21806981353 is an apocalyptic number.

It is an amenable number.

21806981353 is a deficient number, since it is larger than the sum of its proper divisors (1282763627).

21806981353 is a wasteful number, since it uses less digits than its factorization.

21806981353 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1282763626.

The product of its (nonzero) digits is 311040, while the sum is 46.

The spelling of 21806981353 in words is "twenty-one billion, eight hundred six million, nine hundred eighty-one thousand, three hundred fifty-three".