20756751561 has 48 divisors (see below), whose sum is σ = 38091289600. Its totient is φ = 10595422080.

The previous prime is 20756751559. The next prime is 20756751629. The reversal of 20756751561 is 16515765702.

20756751561 is a `hidden beast` number, since 2 + 0 + 75 + 6 + 7 + 515 + 61 = 666.

It is not a de Polignac number, because 20756751561 - 2¹ = 20756751559 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20756751541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 383386 + ... + 434163.

Almost surely, 2^20756751561 is an apocalyptic number.

20756751561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20756751561 is a deficient number, since it is larger than the sum of its proper divisors (17334538039).

20756751561 is a wasteful number, since it uses less digits than its factorization.

20756751561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 817606 (or 817603 counting only the distinct ones).

The product of its (nonzero) digits is 441000, while the sum is 45.

The spelling of 20756751561 in words is "twenty billion, seven hundred fifty-six million, seven hundred fifty-one thousand, five hundred sixty-one".