21573858081 has 4 divisors (see below), whose sum is σ = 28765144112. Its totient is φ = 14382572052.

The previous prime is 21573858077. The next prime is 21573858091. The reversal of 21573858081 is 18085837512.

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 not a de Polignac number, because 21573858081 - 2² = 21573858077 is a prime.

It is a super-2 number, since 2×21573858081² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21573858081.

It is not an unprimeable number, because it can be changed into a prime (21573858091) 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 3 ways as a sum of consecutive naturals, for example, 3595643011 + ... + 3595643016.

It is an arithmetic number, because the mean of its divisors is an integer number (7191286028).

Almost surely, 2^21573858081 is an apocalyptic number.

It is an amenable number.

21573858081 is a deficient number, since it is larger than the sum of its proper divisors (7191286031).

21573858081 is an equidigital number, since it uses as much as digits as its factorization.

21573858081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7191286030.

The product of its (nonzero) digits is 537600, while the sum is 48.

The spelling of 21573858081 in words is "twenty-one billion, five hundred seventy-three million, eight hundred fifty-eight thousand, eighty-one".