21809553617 has 16 divisors (see below), whose sum is σ = 23979696000. Its totient is φ = 19755477504.

The previous prime is 21809553613. The next prime is 21809553629. The reversal of 21809553617 is 71635590812.

It is a cyclic number.

It is not a de Polignac number, because 21809553617 - 2² = 21809553613 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21809553611) 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 15 ways as a sum of consecutive naturals, for example, 135392 + ... + 248897.

It is an arithmetic number, because the mean of its divisors is an integer number (1498731000).

Almost surely, 2^21809553617 is an apocalyptic number.

It is an amenable number.

21809553617 is a deficient number, since it is larger than the sum of its proper divisors (2170142383).

21809553617 is a wasteful number, since it uses less digits than its factorization.

21809553617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 384440.

The product of its (nonzero) digits is 453600, while the sum is 47.

The spelling of 21809553617 in words is "twenty-one billion, eight hundred nine million, five hundred fifty-three thousand, six hundred seventeen".