21121212215 has 4 divisors (see below), whose sum is σ = 25345454664. Its totient is φ = 16896969768.

The previous prime is 21121212209. The next prime is 21121212253. The reversal of 21121212215 is 51221212112.

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 21121212215 - 2²⁴ = 21104434999 is a prime.

It is a super-2 number, since 2×21121212215² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2112121217 + ... + 2112121226.

It is an arithmetic number, because the mean of its divisors is an integer number (6336363666).

Almost surely, 2^21121212215 is an apocalyptic number.

21121212215 is a deficient number, since it is larger than the sum of its proper divisors (4224242449).

21121212215 is an equidigital number, since it uses as much as digits as its factorization.

21121212215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4224242448.

The product of its digits is 160, while the sum is 20.

Adding to 21121212215 its reverse (51221212112), we get a palindrome (72342424327).

The spelling of 21121212215 in words is "twenty-one billion, one hundred twenty-one million, two hundred twelve thousand, two hundred fifteen".