21541780017 has 6 divisors (see below), whose sum is σ = 31115904482. Its totient is φ = 14361186672.

The previous prime is 21541779991. The next prime is 21541780033. The reversal of 21541780017 is 71008714512.

21541780017 is a `hidden beast` number, since 21 + 541 + 7 + 80 + 0 + 17 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19925016336 + 1616763681 = 141156^2 + 40209^2 .

It is not a de Polignac number, because 21541780017 - 2¹² = 21541775921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21541780717) 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 5 ways as a sum of consecutive naturals, for example, 1196765548 + ... + 1196765565.

Almost surely, 2^21541780017 is an apocalyptic number.

It is an amenable number.

21541780017 is a deficient number, since it is larger than the sum of its proper divisors (9574124465).

21541780017 is a wasteful number, since it uses less digits than its factorization.

21541780017 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2393531119 (or 2393531116 counting only the distinct ones).

The product of its (nonzero) digits is 15680, while the sum is 36.

The spelling of 21541780017 in words is "twenty-one billion, five hundred forty-one million, seven hundred eighty thousand, seventeen".