21004351 has 2 divisors, whose sum is σ = 21004352. Its totient is φ = 21004350.

The previous prime is 21004331. The next prime is 21004387. The reversal of 21004351 is 15340012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21004351 - 2¹⁵ = 20971583 is a prime.

It is a congruent number.

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

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502175 + 10502176.

It is an arithmetic number, because the mean of its divisors is an integer number (10502176).

Almost surely, 2^21004351 is an apocalyptic number.

21004351 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004351 is an equidigital number, since it uses as much as digits as its factorization.

21004351 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21004351 is about 4583.0504033886. The cubic root of 21004351 is about 275.9114704161.

Adding to 21004351 its reverse (15340012), we get a palindrome (36344363).

The spelling of 21004351 in words is "twenty-one million, four thousand, three hundred fifty-one".