21258171 has 12 divisors (see below), whose sum is σ = 33497880. Its totient is φ = 12883680.

The previous prime is 21258151. The next prime is 21258173. The reversal of 21258171 is 17185212.

21258171 is a `hidden beast` number, since 2 + 12 + 581 + 71 = 666.

It is not a de Polignac number, because 21258171 - 2¹⁵ = 21225403 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21258173) 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, 107266 + ... + 107463.

It is an arithmetic number, because the mean of its divisors is an integer number (2791490).

Almost surely, 2^21258171 is an apocalyptic number.

21258171 is a deficient number, since it is larger than the sum of its proper divisors (12239709).

21258171 is a wasteful number, since it uses less digits than its factorization.

21258171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214746 (or 214743 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 21258171 is about 4610.6584128517. The cubic root of 21258171 is about 277.0184098943.

It can be divided in two parts, 2125 and 8171, that added together give a triangular number (10296 = T₁₄₃).

The spelling of 21258171 in words is "twenty-one million, two hundred fifty-eight thousand, one hundred seventy-one".