21221213505 has 32 divisors (see below), whose sum is σ = 34193798784. Its totient is φ = 11238130176.

The previous prime is 21221213479. The next prime is 21221213513. The reversal of 21221213505 is 50531212212.

It is not a de Polignac number, because 21221213505 - 2⁵ = 21221213473 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5407474 + ... + 5411396.

It is an arithmetic number, because the mean of its divisors is an integer number (1068556212).

Almost surely, 2^21221213505 is an apocalyptic number.

It is an amenable number.

21221213505 is a deficient number, since it is larger than the sum of its proper divisors (12972585279).

21221213505 is a wasteful number, since it uses less digits than its factorization.

21221213505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6385.

The product of its (nonzero) digits is 1200, while the sum is 24.

Adding to 21221213505 its reverse (50531212212), we get a palindrome (71752425717).

The spelling of 21221213505 in words is "twenty-one billion, two hundred twenty-one million, two hundred thirteen thousand, five hundred five".