20861971749 has 12 divisors (see below), whose sum is σ = 30150714412. Its totient is φ = 13900248000.

The previous prime is 20861971723. The next prime is 20861971751. The reversal of 20861971749 is 94717916802.

20861971749 is a `hidden beast` number, since 2 + 0 + 8 + 619 + 7 + 17 + 4 + 9 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 3512340225 + 17349631524 = 59265^2 + 131718^2 .

It is not a de Polignac number, because 20861971749 - 2⁷ = 20861971621 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20861971695 and 20861971704.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20861971759) 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 11 ways as a sum of consecutive naturals, for example, 627322 + ... + 659739.

Almost surely, 2^20861971749 is an apocalyptic number.

It is an amenable number.

20861971749 is a deficient number, since it is larger than the sum of its proper divisors (9288742663).

20861971749 is a wasteful number, since it uses less digits than its factorization.

20861971749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1288868 (or 1288865 counting only the distinct ones).

The product of its (nonzero) digits is 1524096, while the sum is 54.

It can be divided in two parts, 2086197 and 1749, that added together give a triangular number (2087946 = T₂₀₄₃).

The spelling of 20861971749 in words is "twenty billion, eight hundred sixty-one million, nine hundred seventy-one thousand, seven hundred forty-nine".