21172727 has 4 divisors (see below), whose sum is σ = 21665160. Its totient is φ = 20680296.

The previous prime is 21172717. The next prime is 21172733. The reversal of 21172727 is 72727112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21172727 - 2⁶ = 21172663 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21172727.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172717) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 246152 + ... + 246237.

It is an arithmetic number, because the mean of its divisors is an integer number (5416290).

Almost surely, 2^21172727 is an apocalyptic number.

21172727 is a deficient number, since it is larger than the sum of its proper divisors (492433).

21172727 is an equidigital number, since it uses as much as digits as its factorization.

21172727 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 492432.

The product of its digits is 2744, while the sum is 29.

The square root of 21172727 is about 4601.3831616156. The cubic root of 21172727 is about 276.6467670079.

Adding to 21172727 its reverse (72727112), we get a palindrome (93899839).

The spelling of 21172727 in words is "twenty-one million, one hundred seventy-two thousand, seven hundred twenty-seven".