21106381 has 8 divisors (see below), whose sum is σ = 21926144. Its totient is φ = 20295360.

The previous prime is 21106373. The next prime is 21106399. The reversal of 21106381 is 18360112.

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 21106381 - 2³ = 21106373 is a prime.

It is a super-2 number, since 2×21106381² = 890958637834322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21106301) 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, 2965 + ... + 7141.

It is an arithmetic number, because the mean of its divisors is an integer number (2740768).

Almost surely, 2^21106381 is an apocalyptic number.

It is an amenable number.

21106381 is a deficient number, since it is larger than the sum of its proper divisors (819763).

21106381 is a wasteful number, since it uses less digits than its factorization.

21106381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4371.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 21106381 is about 4594.1681510367. The cubic root of 21106381 is about 276.3575016181.

Adding to 21106381 its reverse (18360112), we get a palindrome (39466493).

The spelling of 21106381 in words is "twenty-one million, one hundred six thousand, three hundred eighty-one".