21215421321 has 16 divisors (see below), whose sum is σ = 29295986688. Its totient is φ = 13647712400.

The previous prime is 21215421319. The next prime is 21215421343. The reversal of 21215421321 is 12312451212.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21215421321 - 2¹ = 21215421319 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21215421291 and 21215421300.

It is not an unprimeable number, because it can be changed into a prime (21215421301) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1049595 + ... + 1069616.

It is an arithmetic number, because the mean of its divisors is an integer number (1830999168).

Almost surely, 2^21215421321 is an apocalyptic number.

It is an amenable number.

21215421321 is a deficient number, since it is larger than the sum of its proper divisors (8080565367).

21215421321 is a wasteful number, since it uses less digits than its factorization.

21215421321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2119332.

The product of its digits is 960, while the sum is 24.

Adding to 21215421321 its reverse (12312451212), we get a palindrome (33527872533).

The spelling of 21215421321 in words is "twenty-one billion, two hundred fifteen million, four hundred twenty-one thousand, three hundred twenty-one".