20175645681 has 27 divisors (see below), whose sum is σ = 29473121899. Its totient is φ = 13299582912.

The previous prime is 20175645673. The next prime is 20175645739. The reversal of 20175645681 is 18654657102.

The square root of 20175645681 is 142041.

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

20175645681 is a `hidden beast` number, since 2 + 0 + 1 + 7 + 564 + 5 + 6 + 81 = 666.

It can be written as a sum of positive squares in only one way, i.e., 355511025 + 19820134656 = 18855^2 + 140784^2 .

It is not a de Polignac number, because 20175645681 - 2³ = 20175645673 is a prime.

It is a super-2 number, since 2×20175645681² (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 (20175645641) 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, 48151690 + ... + 48152108.

Almost surely, 2^20175645681 is an apocalyptic number.

20175645681 is the 142041-st square number.

20175645681 is the 71021-st centered octagonal number.

It is an amenable number.

20175645681 is a deficient number, since it is larger than the sum of its proper divisors (9297476218).

20175645681 is an frugal number, since it uses more digits than its factorization.

20175645681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1070 (or 535 counting only the distinct ones).

The product of its (nonzero) digits is 403200, while the sum is 45.

It can be divided in two parts, 20175 and 645681, that added together give a square (665856 = 816²).

The spelling of 20175645681 in words is "twenty billion, one hundred seventy-five million, six hundred forty-five thousand, six hundred eighty-one".