21716831 has 2 divisors, whose sum is σ = 21716832. Its totient is φ = 21716830.

The previous prime is 21716809. The next prime is 21716857. The reversal of 21716831 is 13861712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21716831 - 2⁶ = 21716767 is a prime.

It is a super-2 number, since 2×21716831² = 943241497365122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21716794 and 21716803.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21716861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10858415 + 10858416.

It is an arithmetic number, because the mean of its divisors is an integer number (10858416).

Almost surely, 2^21716831 is an apocalyptic number.

21716831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21716831 is an equidigital number, since it uses as much as digits as its factorization.

21716831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2016, while the sum is 29.

The square root of 21716831 is about 4660.1320796733. The cubic root of 21716831 is about 278.9965399125.

The spelling of 21716831 in words is "twenty-one million, seven hundred sixteen thousand, eight hundred thirty-one".