20218381 has 2 divisors, whose sum is σ = 20218382. Its totient is φ = 20218380.

The previous prime is 20218379. The next prime is 20218411. The reversal of 20218381 is 18381202.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19096900 + 1121481 = 4370^2 + 1059^2 .

It is a cyclic number.

It is not a de Polignac number, because 20218381 - 2¹ = 20218379 is a prime.

It is a super-2 number, since 2×20218381² = 817565860522322, which contains 22 as substring.

Together with 20218379, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20218361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10109190 + 10109191.

It is an arithmetic number, because the mean of its divisors is an integer number (10109191).

Almost surely, 2^20218381 is an apocalyptic number.

It is an amenable number.

20218381 is a deficient number, since it is larger than the sum of its proper divisors (1).

20218381 is an equidigital number, since it uses as much as digits as its factorization.

20218381 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 20218381 is about 4496.4854052916. The cubic root of 20218381 is about 272.4261495019.

Adding to 20218381 its reverse (18381202), we get a palindrome (38599583).

The spelling of 20218381 in words is "twenty million, two hundred eighteen thousand, three hundred eighty-one".