21912171 has 4 divisors (see below), whose sum is σ = 29216232. Its totient is φ = 14608112.

The previous prime is 21912157. The next prime is 21912173. The reversal of 21912171 is 17121912.

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 21912171 - 2¹¹ = 21910123 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21912173) 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, 3652026 + ... + 3652031.

It is an arithmetic number, because the mean of its divisors is an integer number (7304058).

Almost surely, 2^21912171 is an apocalyptic number.

21912171 is a deficient number, since it is larger than the sum of its proper divisors (7304061).

21912171 is an equidigital number, since it uses as much as digits as its factorization.

21912171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7304060.

The product of its digits is 252, while the sum is 24.

The square root of 21912171 is about 4681.0437938562. The cubic root of 21912171 is about 279.8305564946.

The spelling of 21912171 in words is "twenty-one million, nine hundred twelve thousand, one hundred seventy-one".