21053831 has 2 divisors, whose sum is σ = 21053832. Its totient is φ = 21053830.

The previous prime is 21053783. The next prime is 21053833. The reversal of 21053831 is 13835012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21053831 - 2¹⁴ = 21037447 is a prime.

It is a super-2 number, since 2×21053831² = 886527599553122, which contains 22 as substring.

Together with 21053833, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21053797 and 21053806.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21053833) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10526915 + 10526916.

It is an arithmetic number, because the mean of its divisors is an integer number (10526916).

Almost surely, 2^21053831 is an apocalyptic number.

21053831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21053831 is an equidigital number, since it uses as much as digits as its factorization.

21053831 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21053831 is about 4588.4453794286. The cubic root of 21053831 is about 276.1279556175.

Adding to 21053831 its reverse (13835012), we get a palindrome (34888843).

The spelling of 21053831 in words is "twenty-one million, fifty-three thousand, eight hundred thirty-one".