21004331 has 2 divisors, whose sum is σ = 21004332. Its totient is φ = 21004330.

The previous prime is 21004309. The next prime is 21004351. The reversal of 21004331 is 13340012.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21004331 is a prime.

It is a super-2 number, since 2×21004331² = 882363841515122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21004301) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502165 + 10502166.

It is an arithmetic number, because the mean of its divisors is an integer number (10502166).

Almost surely, 2^21004331 is an apocalyptic number.

21004331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004331 is an equidigital number, since it uses as much as digits as its factorization.

21004331 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 21004331 is about 4583.0482214352. The cubic root of 21004331 is about 275.9113828433.

Adding to 21004331 its reverse (13340012), we get a palindrome (34344343).

The spelling of 21004331 in words is "twenty-one million, four thousand, three hundred thirty-one".