21593420809 has 9 divisors (see below), whose sum is σ = 22576618183. Its totient is φ = 20651343592.

The previous prime is 21593420767. The next prime is 21593420819. The reversal of 21593420809 is 90802439512.

The square root of 21593420809 is 146947.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 60793209 + 21532627600 = 7797^2 + 146740^2 .

It is not a de Polignac number, because 21593420809 - 2⁹ = 21593420297 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21593420819) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 3376587 + ... + 3382975.

Almost surely, 2^21593420809 is an apocalyptic number.

21593420809 is the 146947-th square number.

21593420809 is the 73474-th centered octagonal number.

It is an amenable number.

21593420809 is a deficient number, since it is larger than the sum of its proper divisors (983197374).

21593420809 is an frugal number, since it uses more digits than its factorization.

21593420809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12824 (or 6412 counting only the distinct ones).

The product of its (nonzero) digits is 155520, while the sum is 43.

The spelling of 21593420809 in words is "twenty-one billion, five hundred ninety-three million, four hundred twenty thousand, eight hundred nine".