21216217361 has 4 divisors (see below), whose sum is σ = 22332860400. Its totient is φ = 20099574324.

The previous prime is 21216217349. The next prime is 21216217367. The reversal of 21216217361 is 16371261212.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21216217361 - 2¹⁰ = 21216216337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21216217367) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 558321491 + ... + 558321528.

It is an arithmetic number, because the mean of its divisors is an integer number (5583215100).

Almost surely, 2^21216217361 is an apocalyptic number.

It is an amenable number.

21216217361 is a deficient number, since it is larger than the sum of its proper divisors (1116643039).

21216217361 is a wasteful number, since it uses less digits than its factorization.

21216217361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1116643038.

The product of its digits is 6048, while the sum is 32.

Adding to 21216217361 its reverse (16371261212), we get a palindrome (37587478573).

The spelling of 21216217361 in words is "twenty-one billion, two hundred sixteen million, two hundred seventeen thousand, three hundred sixty-one".