21031312221 has 48 divisors (see below), whose sum is σ = 32821588800. Its totient is φ = 12928495104.

The previous prime is 21031312219. The next prime is 21031312223. The reversal of 21031312221 is 12221313012.

21031312221 is a `hidden beast` number, since 210 + 313 + 122 + 21 = 666.

It is an interprime number because it is at equal distance from previous prime (21031312219) and next prime (21031312223).

It is not a de Polignac number, because 21031312221 - 2¹ = 21031312219 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21031312194 and 21031312203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21031312223) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2767495 + ... + 2775083.

It is an arithmetic number, because the mean of its divisors is an integer number (683783100).

Almost surely, 2^21031312221 is an apocalyptic number.

It is an amenable number.

21031312221 is a deficient number, since it is larger than the sum of its proper divisors (11790276579).

21031312221 is a wasteful number, since it uses less digits than its factorization.

21031312221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7978 (or 7975 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

Adding to 21031312221 its reverse (12221313012), we get a palindrome (33252625233).

The spelling of 21031312221 in words is "twenty-one billion, thirty-one million, three hundred twelve thousand, two hundred twenty-one".