21673831 has 2 divisors, whose sum is σ = 21673832. Its totient is φ = 21673830.

The previous prime is 21673829. The next prime is 21673837. The reversal of 21673831 is 13837612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21673831 - 2¹ = 21673829 is a prime.

It is a super-2 number, since 2×21673831² = 939509900433122, which contains 22 as substring.

Together with 21673829, 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 = 21673793 and 21673802.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21673837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10836915 + 10836916.

It is an arithmetic number, because the mean of its divisors is an integer number (10836916).

Almost surely, 2^21673831 is an apocalyptic number.

21673831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21673831 is an equidigital number, since it uses as much as digits as its factorization.

21673831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6048, while the sum is 31.

The square root of 21673831 is about 4655.5161904992. The cubic root of 21673831 is about 278.8122776386.

It can be divided in two parts, 216 and 73831, that added together give a palindrome (74047).

The spelling of 21673831 in words is "twenty-one million, six hundred seventy-three thousand, eight hundred thirty-one".