21103172 has 12 divisors (see below), whose sum is σ = 37928940. Its totient is φ = 10266336.

The previous prime is 21103139. The next prime is 21103177. The reversal of 21103172 is 27130112.

It can be written as a sum of positive squares in 2 ways, for example, as 8386816 + 12716356 = 2896^2 + 3566^2 .

It is a super-3 number, since 3×21103172³ (a number of 23 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21103172.

It is not an unprimeable number, because it can be changed into a prime (21103177) 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, 71147 + ... + 71442.

It is an arithmetic number, because the mean of its divisors is an integer number (3160745).

Almost surely, 2^21103172 is an apocalyptic number.

It is an amenable number.

21103172 is a deficient number, since it is larger than the sum of its proper divisors (16825768).

21103172 is a wasteful number, since it uses less digits than its factorization.

21103172 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 142630 (or 142628 counting only the distinct ones).

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21103172 is about 4593.8188906399. The cubic root of 21103172 is about 276.3434951719.

Adding to 21103172 its reverse (27130112), we get a palindrome (48233284).

It can be divided in two parts, 21 and 103172, that multiplied together give a palindrome (2166612).

The spelling of 21103172 in words is "twenty-one million, one hundred three thousand, one hundred seventy-two".