21321031 has 2 divisors, whose sum is σ = 21321032. Its totient is φ = 21321030.

The previous prime is 21321019. The next prime is 21321067. The reversal of 21321031 is 13012312.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21321031 is a prime.

It is a super-2 number, since 2×21321031² = 909172725805922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21321331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660515 + 10660516.

It is an arithmetic number, because the mean of its divisors is an integer number (10660516).

Almost surely, 2^21321031 is an apocalyptic number.

21321031 is a deficient number, since it is larger than the sum of its proper divisors (1).

21321031 is an equidigital number, since it uses as much as digits as its factorization.

21321031 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21321031 is about 4617.4701948145. The cubic root of 21321031 is about 277.2911872296.

Adding to 21321031 its reverse (13012312), we get a palindrome (34333343).

The spelling of 21321031 in words is "twenty-one million, three hundred twenty-one thousand, thirty-one".