21521432215 has 4 divisors (see below), whose sum is σ = 25825718664. Its totient is φ = 17217145768.

The previous prime is 21521432213. The next prime is 21521432291. The reversal of 21521432215 is 51223412512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21521432215 - 2¹ = 21521432213 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521432213) 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 3 ways as a sum of consecutive naturals, for example, 2152143217 + ... + 2152143226.

It is an arithmetic number, because the mean of its divisors is an integer number (6456429666).

Almost surely, 2^21521432215 is an apocalyptic number.

21521432215 is a deficient number, since it is larger than the sum of its proper divisors (4304286449).

21521432215 is an equidigital number, since it uses as much as digits as its factorization.

21521432215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4304286448.

The product of its digits is 4800, while the sum is 28.

Adding to 21521432215 its reverse (51223412512), we get a palindrome (72744844727).

The spelling of 21521432215 in words is "twenty-one billion, five hundred twenty-one million, four hundred thirty-two thousand, two hundred fifteen".