21717172 has 12 divisors (see below), whose sum is σ = 39315780. Its totient is φ = 10484096.

The previous prime is 21717169. The next prime is 21717191. The reversal of 21717172 is 27171712.

It can be written as a sum of positive squares in 2 ways, for example, as 13571856 + 8145316 = 3684^2 + 2854^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21717172.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 93493 + ... + 93724.

It is an arithmetic number, because the mean of its divisors is an integer number (3276315).

Almost surely, 2^21717172 is an apocalyptic number.

It is an amenable number.

21717172 is a deficient number, since it is larger than the sum of its proper divisors (17598608).

21717172 is a wasteful number, since it uses less digits than its factorization.

21717172 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 187250 (or 187248 counting only the distinct ones).

The product of its digits is 1372, while the sum is 28.

The square root of 21717172 is about 4660.1686664755. The cubic root of 21717172 is about 278.9980001826.

Adding to 21717172 its reverse (27171712), we get a palindrome (48888884).

It can be divided in two parts, 2171717 and 2, that multiplied together give a palindrome (4343434).

The spelling of 21717172 in words is "twenty-one million, seven hundred seventeen thousand, one hundred seventy-two".