21402171 has 32 divisors (see below), whose sum is σ = 36992000. Its totient is φ = 12224520.

The previous prime is 21402163. The next prime is 21402181. The reversal of 21402171 is 17120412.

It is not a de Polignac number, because 21402171 - 2³ = 21402163 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21402181) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8106 + ... + 10416.

It is an arithmetic number, because the mean of its divisors is an integer number (1156000).

Almost surely, 2^21402171 is an apocalyptic number.

21402171 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21402171 is a deficient number, since it is larger than the sum of its proper divisors (15589829).

21402171 is an equidigital number, since it uses as much as digits as its factorization.

21402171 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2341 (or 2321 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 21402171 is about 4626.2480478245. The cubic root of 21402171 is about 277.6424980337.

Subtracting from 21402171 its sum of digits (18), we obtain a triangular number (21402153 = T₆₅₄₂).

Adding to 21402171 its reverse (17120412), we get a palindrome (38522583).

The spelling of 21402171 in words is "twenty-one million, four hundred two thousand, one hundred seventy-one".