21838681 has 4 divisors (see below), whose sum is σ = 22115200. Its totient is φ = 21562164.

The previous prime is 21838679. The next prime is 21838723. The reversal of 21838681 is 18683812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21838681 - 2¹ = 21838679 is a prime.

It is a super-2 number, since 2×21838681² = 953855975639522, which contains 22 as substring.

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 21838681.

It is not an unprimeable number, because it can be changed into a prime (21838631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 138141 + ... + 138298.

It is an arithmetic number, because the mean of its divisors is an integer number (5528800).

Almost surely, 2^21838681 is an apocalyptic number.

It is an amenable number.

21838681 is a deficient number, since it is larger than the sum of its proper divisors (276519).

21838681 is an equidigital number, since it uses as much as digits as its factorization.

21838681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 276518.

The product of its digits is 18432, while the sum is 37.

The square root of 21838681 is about 4673.1874561160. The cubic root of 21838681 is about 279.5173701100.

The spelling of 21838681 in words is "twenty-one million, eight hundred thirty-eight thousand, six hundred eighty-one".