21217868577 has 6 divisors (see below), whose sum is σ = 30648032402. Its totient is φ = 14145245712.

The previous prime is 21217868557. The next prime is 21217868587. The reversal of 21217868577 is 77586871212.

21217868577 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 7 + 8 + 68 + 577 = 666.

It can be written as a sum of positive squares in only one way, i.e., 13623791841 + 7594076736 = 116721^2 + 87144^2 .

It is not a de Polignac number, because 21217868577 - 2¹⁰ = 21217867553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21217868557) 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, 1178770468 + ... + 1178770485.

Almost surely, 2^21217868577 is an apocalyptic number.

It is an amenable number.

21217868577 is a deficient number, since it is larger than the sum of its proper divisors (9430163825).

21217868577 is a wasteful number, since it uses less digits than its factorization.

21217868577 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2357540959 (or 2357540956 counting only the distinct ones).

The product of its digits is 2634240, while the sum is 54.

The spelling of 21217868577 in words is "twenty-one billion, two hundred seventeen million, eight hundred sixty-eight thousand, five hundred seventy-seven".