21564217719 has 24 divisors (see below), whose sum is σ = 34239389184. Its totient is φ = 12969450000.

The previous prime is 21564217693. The next prime is 21564217733. The reversal of 21564217719 is 91771246512.

21564217719 is a `hidden beast` number, since 2 + 1 + 564 + 2 + 1 + 77 + 19 = 666.

It is not a de Polignac number, because 21564217719 - 2¹² = 21564213623 is a prime.

It is a super-2 number, since 2×21564217719² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21564217819) 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 23 ways as a sum of consecutive naturals, for example, 818407 + ... + 844344.

It is an arithmetic number, because the mean of its divisors is an integer number (1426641216).

Almost surely, 2^21564217719 is an apocalyptic number.

21564217719 is a deficient number, since it is larger than the sum of its proper divisors (12675171465).

21564217719 is a wasteful number, since it uses less digits than its factorization.

21564217719 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1662899 (or 1662896 counting only the distinct ones).

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

The spelling of 21564217719 in words is "twenty-one billion, five hundred sixty-four million, two hundred seventeen thousand, seven hundred nineteen".