21809553615 has 32 divisors (see below), whose sum is σ = 39820455360. Its totient is φ = 11317387392.

The previous prime is 21809553613. The next prime is 21809553629. The reversal of 21809553615 is 51635590812.

21809553615 is a `hidden beast` number, since 2 + 1 + 80 + 9 + 553 + 6 + 15 = 666.

It is not a de Polignac number, because 21809553615 - 2¹ = 21809553613 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent 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 (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2178144 + ... + 2188133.

It is an arithmetic number, because the mean of its divisors is an integer number (1244389230).

Almost surely, 2^21809553615 is an apocalyptic number.

21809553615 is a deficient number, since it is larger than the sum of its proper divisors (18010901745).

21809553615 is a wasteful number, since it uses less digits than its factorization.

21809553615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4366328 (or 4366322 counting only the distinct ones).

The product of its (nonzero) digits is 324000, while the sum is 45.

The spelling of 21809553615 in words is "twenty-one billion, eight hundred nine million, five hundred fifty-three thousand, six hundred fifteen".