21424831 has 2 divisors, whose sum is σ = 21424832. Its totient is φ = 21424830.

The previous prime is 21424829. The next prime is 21424841. The reversal of 21424831 is 13842412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21424831 - 2¹ = 21424829 is a prime.

It is a super-2 number, since 2×21424831² = 918046766757122, which contains 22 as substring.

Together with 21424829, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21424796 and 21424805.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21424841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10712415 + 10712416.

It is an arithmetic number, because the mean of its divisors is an integer number (10712416).

Almost surely, 2^21424831 is an apocalyptic number.

21424831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21424831 is an equidigital number, since it uses as much as digits as its factorization.

21424831 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1536, while the sum is 25.

The square root of 21424831 is about 4628.6964687696. The cubic root of 21424831 is about 277.7404500893.

The spelling of 21424831 in words is "twenty-one million, four hundred twenty-four thousand, eight hundred thirty-one".