21706871 has 4 divisors (see below), whose sum is σ = 22650672. Its totient is φ = 20763072.

The previous prime is 21706837. The next prime is 21706889. The reversal of 21706871 is 17860712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21706871 - 2¹⁸ = 21444727 is a prime.

It is a super-2 number, since 2×21706871² = 942376497221282, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21706891) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 471866 + ... + 471911.

It is an arithmetic number, because the mean of its divisors is an integer number (5662668).

Almost surely, 2^21706871 is an apocalyptic number.

21706871 is a deficient number, since it is larger than the sum of its proper divisors (943801).

21706871 is an equidigital number, since it uses as much as digits as its factorization.

21706871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 943800.

The product of its (nonzero) digits is 4704, while the sum is 32.

The square root of 21706871 is about 4659.0633178784. The cubic root of 21706871 is about 278.9538812873.

The spelling of 21706871 in words is "twenty-one million, seven hundred six thousand, eight hundred seventy-one".