20718855929209 has 9 divisors (see below), whose sum is σ = 20754059990853. Its totient is φ = 20683711504572.

The previous prime is 20718855929201. The next prime is 20718855929231. The reversal of 20718855929209 is 90292955881702.

The square root of 20718855929209 is 4551797.

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

It is not a de Polignac number, because 20718855929209 - 2³ = 20718855929201 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20718855929201) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2926801932 + ... + 2926809010.

Almost surely, 2^{20718855929209} is an apocalyptic number.

20718855929209 is the 4551797-th square number.

20718855929209 is the 2275899-th centered octagonal number.

It is an amenable number.

20718855929209 is a deficient number, since it is larger than the sum of its proper divisors (35204061644).

20718855929209 is an frugal number, since it uses more digits than its factorization.

20718855929209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15444 (or 7722 counting only the distinct ones).

The product of its (nonzero) digits is 65318400, while the sum is 67.

The spelling of 20718855929209 in words is "twenty trillion, seven hundred eighteen billion, eight hundred fifty-five million, nine hundred twenty-nine thousand, two hundred nine".