21154171 has 4 divisors (see below), whose sum is σ = 22398552. Its totient is φ = 19909792.

The previous prime is 21154157. The next prime is 21154187. The reversal of 21154171 is 17145112.

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 21154171 - 2⁵ = 21154139 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21154141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 622165 + ... + 622198.

It is an arithmetic number, because the mean of its divisors is an integer number (5599638).

Almost surely, 2^21154171 is an apocalyptic number.

21154171 is a deficient number, since it is larger than the sum of its proper divisors (1244381).

21154171 is a wasteful number, since it uses less digits than its factorization.

21154171 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1244380.

The product of its digits is 280, while the sum is 22.

The square root of 21154171 is about 4599.3663694035. The cubic root of 21154171 is about 276.5659246770.

Adding to 21154171 its reverse (17145112), we get a palindrome (38299283).

The spelling of 21154171 in words is "twenty-one million, one hundred fifty-four thousand, one hundred seventy-one".