21616161 has 8 divisors (see below), whose sum is σ = 32938944. Its totient is φ = 12352080.

The previous prime is 21616157. The next prime is 21616169. The reversal of 21616161 is 16161612.

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

It is not a de Polignac number, because 21616161 - 2² = 21616157 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21616169) 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 7 ways as a sum of consecutive naturals, for example, 514650 + ... + 514691.

It is an arithmetic number, because the mean of its divisors is an integer number (4117368).

Almost surely, 2^21616161 is an apocalyptic number.

21616161 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21616161 is a deficient number, since it is larger than the sum of its proper divisors (11322783).

21616161 is a wasteful number, since it uses less digits than its factorization.

21616161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1029351.

The product of its digits is 432, while the sum is 24.

The square root of 21616161 is about 4649.3183371329. The cubic root of 21616161 is about 278.5647689213.

Adding to 21616161 its reverse (16161612), we get a palindrome (37777773).

The spelling of 21616161 in words is "twenty-one million, six hundred sixteen thousand, one hundred sixty-one".