21306172 has 12 divisors (see below), whose sum is σ = 37355976. Its totient is φ = 10633040.

The previous prime is 21306169. The next prime is 21306179. The reversal of 21306172 is 27160312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21306179) 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, 2479 + ... + 6982.

It is an arithmetic number, because the mean of its divisors is an integer number (3112998).

Almost surely, 2^21306172 is an apocalyptic number.

It is an amenable number.

21306172 is a deficient number, since it is larger than the sum of its proper divisors (16049804).

21306172 is a wasteful number, since it uses less digits than its factorization.

21306172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10028 (or 10026 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21306172 is about 4615.8609164488. The cubic root of 21306172 is about 277.2267558975.

Adding to 21306172 its reverse (27160312), we get a palindrome (48466484).

The spelling of 21306172 in words is "twenty-one million, three hundred six thousand, one hundred seventy-two".