20409278981569 has 9 divisors (see below), whose sum is σ = 20975961076707. Its totient is φ = 19857514211064.

The previous prime is 20409278981561. The next prime is 20409278981579. The reversal of 20409278981569 is 96518987290402.

The square root of 20409278981569 is 4517663.

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., 18262503106225 + 2146775875344 = 4273465^2 + 1465188^2 .

It is not a de Polignac number, because 20409278981569 - 2³ = 20409278981561 is a prime.

It is a super-2 number, since 2×20409278981569² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20409278981498 and 20409278981507.

It is not an unprimeable number, because it can be changed into a prime (20409278981561) 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, 167092482 + ... + 167214580.

Almost surely, 2^{20409278981569} is an apocalyptic number.

20409278981569 is the 4517663-rd square number.

20409278981569 is the 2258832-nd centered octagonal number.

It is an amenable number.

20409278981569 is a deficient number, since it is larger than the sum of its proper divisors (566682095138).

20409278981569 is an frugal number, since it uses more digits than its factorization.

20409278981569 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 244272 (or 122136 counting only the distinct ones).

The product of its (nonzero) digits is 156764160, while the sum is 70.

The spelling of 20409278981569 in words is "twenty trillion, four hundred nine billion, two hundred seventy-eight million, nine hundred eighty-one thousand, five hundred sixty-nine".