21511031213221 has 32 divisors (see below), whose sum is σ = 24084361929600. Its totient is φ = 19046100602880.

The previous prime is 21511031213219. The next prime is 21511031213281. The reversal of 21511031213221 is 12231213011512.

It is a cyclic number.

It is not a de Polignac number, because 21511031213221 - 2¹ = 21511031213219 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21511031213201) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1096988065 + ... + 1097007673.

It is an arithmetic number, because the mean of its divisors is an integer number (752636310300).

Almost surely, 2^{21511031213221} is an apocalyptic number.

It is an amenable number.

21511031213221 is a deficient number, since it is larger than the sum of its proper divisors (2573330716379).

21511031213221 is a wasteful number, since it uses less digits than its factorization.

21511031213221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33349.

The product of its (nonzero) digits is 720, while the sum is 25.

Adding to 21511031213221 its reverse (12231213011512), we get a palindrome (33742244224733).

The spelling of 21511031213221 in words is "twenty-one trillion, five hundred eleven billion, thirty-one million, two hundred thirteen thousand, two hundred twenty-one".