20823355809 has 27 divisors (see below), whose sum is σ = 30438214833. Its totient is φ = 13718020392.

The previous prime is 20823355799. The next prime is 20823355823. The reversal of 20823355809 is 90855332802.

The square root of 20823355809 is 144303.

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

It is a de Polignac number, because none of the positive numbers 2^k-20823355809 is a prime.

It is a super-2 number, since 2×20823355809² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20823355849) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 44589394 + ... + 44589860.

Almost surely, 2^20823355809 is an apocalyptic number.

20823355809 is the 144303-rd square number.

20823355809 is the 72152-nd centered octagonal number.

It is an amenable number.

20823355809 is a deficient number, since it is larger than the sum of its proper divisors (9614859024).

20823355809 is an frugal number, since it uses more digits than its factorization.

20823355809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1146 (or 573 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 45.

The spelling of 20823355809 in words is "twenty billion, eight hundred twenty-three million, three hundred fifty-five thousand, eight hundred nine".