21591000905 has 8 divisors (see below), whose sum is σ = 26609449992. Its totient is φ = 16805968128.

The previous prime is 21591000901. The next prime is 21591000919. The reversal of 21591000905 is 50900019512.

It can be written as a sum of positive squares in 4 ways, for example, as 664195984 + 20926804921 = 25772^2 + 144661^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21591000905 - 2² = 21591000901 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21591000901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 58353872 + ... + 58354241.

It is an arithmetic number, because the mean of its divisors is an integer number (3326181249).

Almost surely, 2^21591000905 is an apocalyptic number.

It is an amenable number.

21591000905 is a deficient number, since it is larger than the sum of its proper divisors (5018449087).

21591000905 is a wasteful number, since it uses less digits than its factorization.

21591000905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116708155.

The product of its (nonzero) digits is 4050, while the sum is 32.

The spelling of 21591000905 in words is "twenty-one billion, five hundred ninety-one million, nine hundred five", and thus it is an aban number.