21172109 has 8 divisors (see below), whose sum is σ = 24243648. Its totient is φ = 18112320.

The previous prime is 21172097. The next prime is 21172133. The reversal of 21172109 is 90127112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21172109 - 2¹⁶ = 21106573 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172139) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1349 + ... + 6645.

It is an arithmetic number, because the mean of its divisors is an integer number (3030456).

Almost surely, 2^21172109 is an apocalyptic number.

It is an amenable number.

21172109 is a deficient number, since it is larger than the sum of its proper divisors (3071539).

21172109 is an equidigital number, since it uses as much as digits as its factorization.

21172109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5875.

The product of its (nonzero) digits is 252, while the sum is 23.

The square root of 21172109 is about 4601.3160074048. The cubic root of 21172109 is about 276.6440753477.

The spelling of 21172109 in words is "twenty-one million, one hundred seventy-two thousand, one hundred nine".