21405233217 has 16 divisors (see below), whose sum is σ = 29184442560. Its totient is φ = 13950763200.

The previous prime is 21405233209. The next prime is 21405233249. The reversal of 21405233217 is 71233250412.

It is not a de Polignac number, because 21405233217 - 2³ = 21405233209 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21405233207) 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 15 ways as a sum of consecutive naturals, for example, 302034 + ... + 366107.

It is an arithmetic number, because the mean of its divisors is an integer number (1824027660).

Almost surely, 2^21405233217 is an apocalyptic number.

It is an amenable number.

21405233217 is a deficient number, since it is larger than the sum of its proper divisors (7779209343).

21405233217 is a wasteful number, since it uses less digits than its factorization.

21405233217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668384.

The product of its (nonzero) digits is 10080, while the sum is 30.

Adding to 21405233217 its reverse (71233250412), we get a palindrome (92638483629).

The spelling of 21405233217 in words is "twenty-one billion, four hundred five million, two hundred thirty-three thousand, two hundred seventeen".