21004831 has 2 divisors, whose sum is σ = 21004832. Its totient is φ = 21004830.

The previous prime is 21004829. The next prime is 21004847. The reversal of 21004831 is 13840012.

21004831 is nontrivially palindromic in base 15.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21004831 - 2¹ = 21004829 is a prime.

It is a super-2 number, since 2×21004831² = 882405850677122, which contains 22 as substring.

Together with 21004829, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21004799 and 21004808.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21004811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502415 + 10502416.

It is an arithmetic number, because the mean of its divisors is an integer number (10502416).

Almost surely, 2^21004831 is an apocalyptic number.

21004831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004831 is an equidigital number, since it uses as much as digits as its factorization.

21004831 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21004831 is about 4583.1027699584. The cubic root of 21004831 is about 275.9135721473.

Adding to 21004831 its reverse (13840012), we get a palindrome (34844843).

The spelling of 21004831 in words is "twenty-one million, four thousand, eight hundred thirty-one".