21661727 has 4 divisors (see below), whose sum is σ = 21671640. Its totient is φ = 21651816.

The previous prime is 21661711. The next prime is 21661733. The reversal of 21661727 is 72716612.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21661727 - 2⁴ = 21661711 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21661693 and 21661702.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661027) by changing a digit.

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, 77 + ... + 6582.

It is an arithmetic number, because the mean of its divisors is an integer number (5417910).

Almost surely, 2^21661727 is an apocalyptic number.

21661727 is a deficient number, since it is larger than the sum of its proper divisors (9913).

21661727 is an equidigital number, since it uses as much as digits as its factorization.

21661727 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9912.

The product of its digits is 7056, while the sum is 32.

The square root of 21661727 is about 4654.2160456945. The cubic root of 21661727 is about 278.7603660003.

The spelling of 21661727 in words is "twenty-one million, six hundred sixty-one thousand, seven hundred twenty-seven".