21026831 has 6 divisors (see below), whose sum is σ = 24459840. Its totient is φ = 18022956.

The previous prime is 21026821. The next prime is 21026839. The reversal of 21026831 is 13862012.

It is a de Polignac number, because none of the positive numbers 2^k-21026831 is a prime.

It is a super-2 number, since 2×21026831² = 884255243805122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21026797 and 21026806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21026839) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 214511 + ... + 214608.

It is an arithmetic number, because the mean of its divisors is an integer number (4076640).

Almost surely, 2^21026831 is an apocalyptic number.

21026831 is a deficient number, since it is larger than the sum of its proper divisors (3433009).

21026831 is an equidigital number, since it uses as much as digits as its factorization.

21026831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 429133 (or 429126 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21026831 is about 4585.5022625662. The cubic root of 21026831 is about 276.0098671471.

Adding to 21026831 its reverse (13862012), we get a palindrome (34888843).

The spelling of 21026831 in words is "twenty-one million, twenty-six thousand, eight hundred thirty-one".