21749521761 has 128 divisors (see below), whose sum is σ = 38957760000. Its totient is φ = 11836661760.

The previous prime is 21749521753. The next prime is 21749521777. The reversal of 21749521761 is 16712594712.

21749521761 is a `hidden beast` number, since 2 + 17 + 49 + 521 + 76 + 1 = 666.

It is not a de Polignac number, because 21749521761 - 2³ = 21749521753 is a prime.

It is a super-2 number, since 2×21749521761² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21749571761) 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 127 ways as a sum of consecutive naturals, for example, 13030635 + ... + 13032303.

It is an arithmetic number, because the mean of its divisors is an integer number (304357500).

Almost surely, 2^21749521761 is an apocalyptic number.

It is an amenable number.

21749521761 is a deficient number, since it is larger than the sum of its proper divisors (17208238239).

21749521761 is a wasteful number, since it uses less digits than its factorization.

21749521761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1824 (or 1818 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The spelling of 21749521761 in words is "twenty-one billion, seven hundred forty-nine million, five hundred twenty-one thousand, seven hundred sixty-one".