20818381 has 4 divisors (see below), whose sum is σ = 21723552. Its totient is φ = 19913212.

The previous prime is 20818379. The next prime is 20818403. The reversal of 20818381 is 18381802.

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 20818381 - 2¹ = 20818379 is a prime.

It is a super-2 number, since 2×20818381² = 866809974922322, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20818351) 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, 452551 + ... + 452596.

It is an arithmetic number, because the mean of its divisors is an integer number (5430888).

Almost surely, 2^20818381 is an apocalyptic number.

It is an amenable number.

20818381 is a deficient number, since it is larger than the sum of its proper divisors (905171).

20818381 is an equidigital number, since it uses as much as digits as its factorization.

20818381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 905170.

The product of its (nonzero) digits is 3072, while the sum is 31.

The square root of 20818381 is about 4562.7164058267. The cubic root of 20818381 is about 275.0947596304.

The spelling of 20818381 in words is "twenty million, eight hundred eighteen thousand, three hundred eighty-one".