21517894473 has 4 divisors (see below), whose sum is σ = 28690525968. Its totient is φ = 14345262980.

The previous prime is 21517894471. The next prime is 21517894487. The reversal of 21517894473 is 37449871512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21517894473 - 2¹ = 21517894471 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21517894471) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3586315743 + ... + 3586315748.

It is an arithmetic number, because the mean of its divisors is an integer number (7172631492).

Almost surely, 2^21517894473 is an apocalyptic number.

It is an amenable number.

21517894473 is a deficient number, since it is larger than the sum of its proper divisors (7172631495).

21517894473 is an equidigital number, since it uses as much as digits as its factorization.

21517894473 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7172631494.

The product of its digits is 1693440, while the sum is 51.

The spelling of 21517894473 in words is "twenty-one billion, five hundred seventeen million, eight hundred ninety-four thousand, four hundred seventy-three".