21109671 has 12 divisors (see below), whose sum is σ = 33263880. Its totient is φ = 12793680.

The previous prime is 21109661. The next prime is 21109679. The reversal of 21109671 is 17690112.

It is not a de Polignac number, because 21109671 - 2⁹ = 21109159 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21109679) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 106516 + ... + 106713.

It is an arithmetic number, because the mean of its divisors is an integer number (2771990).

Almost surely, 2^21109671 is an apocalyptic number.

21109671 is a deficient number, since it is larger than the sum of its proper divisors (12154209).

21109671 is a wasteful number, since it uses less digits than its factorization.

21109671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213246 (or 213243 counting only the distinct ones).

The product of its (nonzero) digits is 756, while the sum is 27.

The square root of 21109671 is about 4594.5261997294. The cubic root of 21109671 is about 276.3718601343.

Adding to 21109671 its reverse (17690112), we get a palindrome (38799783).

It can be divided in two parts, 2110 and 9671, that added together give a triangular number (11781 = T₁₅₃).

The spelling of 21109671 in words is "twenty-one million, one hundred nine thousand, six hundred seventy-one".