21207331 has 2 divisors, whose sum is σ = 21207332. Its totient is φ = 21207330.

The previous prime is 21207301. The next prime is 21207341. The reversal of 21207331 is 13370212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21207331 - 2¹⁵ = 21174563 is a prime.

It is a super-2 number, since 2×21207331² = 899501776287122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21207299 and 21207308.

It is not a weakly prime, because it can be changed into another prime (21207301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10603665 + 10603666.

It is an arithmetic number, because the mean of its divisors is an integer number (10603666).

Almost surely, 2^21207331 is an apocalyptic number.

21207331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21207331 is an equidigital number, since it uses as much as digits as its factorization.

21207331 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 252, while the sum is 19.

The square root of 21207331 is about 4605.1418002055. The cubic root of 21207331 is about 276.7973990631.

Adding to 21207331 its reverse (13370212), we get a palindrome (34577543).

The spelling of 21207331 in words is "twenty-one million, two hundred seven thousand, three hundred thirty-one".