20905400569 has 9 divisors (see below), whose sum is σ = 21043224111. Its totient is φ = 20768476680.

The previous prime is 20905400567. The next prime is 20905400597. The reversal of 20905400569 is 96500450902.

The square root of 20905400569 is 144587.

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., 12915186025 + 7990214544 = 113645^2 + 89388^2 .

It is not a de Polignac number, because 20905400569 - 2¹ = 20905400567 is a prime.

It is a super-2 number, since 2×20905400569² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20905400561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 27615739 + ... + 27616495.

Almost surely, 2^20905400569 is an apocalyptic number.

20905400569 is the 144587-th square number.

20905400569 is the 72294-th centered octagonal number.

It is an amenable number.

20905400569 is a deficient number, since it is larger than the sum of its proper divisors (137823542).

20905400569 is an frugal number, since it uses more digits than its factorization.

20905400569 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1896 (or 948 counting only the distinct ones).

The product of its (nonzero) digits is 97200, while the sum is 40.

The spelling of 20905400569 in words is "twenty billion, nine hundred five million, four hundred thousand, five hundred sixty-nine".