21198381 has 8 divisors (see below), whose sum is σ = 28331520. Its totient is φ = 14098752.

The previous prime is 21198377. The next prime is 21198407. The reversal of 21198381 is 18389112.

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

It is not a de Polignac number, because 21198381 - 2² = 21198377 is a prime.

It is a super-2 number, since 2×21198381² = 898742714042322, which contains 22 as substring.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21191381) 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 7 ways as a sum of consecutive naturals, for example, 6861 + ... + 9458.

It is an arithmetic number, because the mean of its divisors is an integer number (3541440).

Almost surely, 2^21198381 is an apocalyptic number.

It is an amenable number.

21198381 is a deficient number, since it is larger than the sum of its proper divisors (7133139).

21198381 is a wasteful number, since it uses less digits than its factorization.

21198381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16755.

The product of its digits is 3456, while the sum is 33.

The square root of 21198381 is about 4604.1699577665. The cubic root of 21198381 is about 276.7584552139.

The spelling of 21198381 in words is "twenty-one million, one hundred ninety-eight thousand, three hundred eighty-one".