21424543665 has 24 divisors (see below), whose sum is σ = 39875886720. Its totient is φ = 9794076768.

The previous prime is 21424543663. The next prime is 21424543711. The reversal of 21424543665 is 56634542412.

It is a happy number.

It is not a de Polignac number, because 21424543665 - 2¹ = 21424543663 is a prime.

It is a super-2 number, since 2×21424543665² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21424543663) 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 23 ways as a sum of consecutive naturals, for example, 14573785 + ... + 14575254.

It is an arithmetic number, because the mean of its divisors is an integer number (1661495280).

Almost surely, 2^21424543665 is an apocalyptic number.

It is an amenable number.

21424543665 is a deficient number, since it is larger than the sum of its proper divisors (18451343055).

21424543665 is a wasteful number, since it uses less digits than its factorization.

21424543665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29149061 (or 29149054 counting only the distinct ones).

The product of its digits is 691200, while the sum is 42.

The spelling of 21424543665 in words is "twenty-one billion, four hundred twenty-four million, five hundred forty-three thousand, six hundred sixty-five".